To speak and write fluently, you need to connect ideas logically and clearly. This unit focuses on sentence complexity: how to build longer, more detailed, and more nuanced sentences using linking devices, conjunctions, relative clauses, and adverbial phrases.
You’ll practice combining simple ideas into complex statements, using connectors like although, because, while, in order to, and however. We’ll also cover gerunds and infinitives, purpose and result structures, and techniques to add variety and fluency to your communication. This unit helps you sound more sophisticated and articulate, especially in written tasks, presentations, and debates.

18.1 SENTENCE TYPES: SIMPLE, COMPOUND, COMPLEX
Objective:
To understand and differentiate between simple, compound, and complex sentences, and to learn how to use them to improve writing fluency and clarity in English.
🔹 1. SIMPLE SENTENCES
A simple sentence contains one independent clause (a subject and a verb) and expresses a complete idea.
Structure    Example
Subject + Verb    She studies every day.
Subject + Verb + Object    I like chocolate.
Subject + Verb + Complement    He is a teacher.
✅ Simple sentences may include adjectives, adverbs, and objects, but they have only one clause.

🔸 2. COMPOUND SENTENCES
A compound sentence contains two independent clauses joined by a coordinating conjunction (for, and, nor, but, or, yet, so — acronym: FANBOYS).
Structure    Example
Clause 1 + , + FANBOYS + Clause 2    She wanted to go out, but it was raining.
Clause 1 + ; + Clause 2    It’s late; we should go home.
✅ Each clause could stand alone as a full sentence.

🔹 3. COMPLEX SENTENCES
A complex sentence contains one independent clause and at least one dependent clause introduced by a subordinating conjunction (e.g., because, although, when, if, since, while, etc.).
Structure    Example
Subordinator + Dependent Clause + , + Main Clause    Although it was late, she kept working.
Main Clause + Subordinator + Dependent Clause    She kept working although it was late.
✅ The dependent clause does not express a complete idea on its own.

🔸 COMMON SUBORDINATING CONJUNCTIONS
Type    Examples
Time    when, while, after, before, until
Cause/Effect    because, since, as
Contrast    although, though, even though
Condition    if, unless, in case

🔹 SENTENCE TYPE COMPARISON
Sentence Type    Example
Simple    I go to the gym.
Compound    I go to the gym, and I eat healthy.
Complex    I go to the gym because I want to stay fit.
✅ Using a mix of all three improves writing style and coherence.

🧠 SENTENCE CONSTRUCTION TIPS
Use simple sentences for clarity and impact
Use compound sentences to connect equal ideas
Use complex sentences to explain, contrast, or add detail

❗ COMMON MISTAKES
Mistake    Correction    Why?
She go to work, and study English.    She goes to work and studies English.    Subject-verb agreement + parallel structure
I like coffee, because it's hot.    ✔ Correct (but avoid comma before “because”)    Don’t use a comma before "because" unless necessary for clarity
Although she tired, she stayed.    Although she was tired, she stayed.    Verb missing in the dependent clause

💬 EXAMPLE DIALOG
Elisa: How do you organize your day?
Victor: I wake up early. (simple)
Elisa: And after that?
Victor: I make coffee, and I read the news. (compound)
Elisa: Sounds relaxing!
Victor: It is, although I sometimes work while I eat. (complex)

18.2 COORDINATING AND SUBORDINATING CONJUNCTIONS
Objective:
To understand how to use coordinating and subordinating conjunctions to connect ideas, form longer sentences, and improve fluency and coherence in writing and speaking.

🔹 COORDINATING CONJUNCTIONS (FANBOYS)
Used to join two independent clauses (complete sentences) of equal importance.
Conjunction    Use    Example
for    reason    He stayed home, for he was sick.
and    addition    She plays guitar, and she sings too.
nor    negative alternative    He doesn’t drink coffee, nor does he like tea.
but    contrast    It’s cold, but we’re going out anyway.
or    choice    You can walk, or you can take a taxi.
yet    contrast (like “but”)    She was tired, yet she finished the job.
so    result/consequence    It rained, so we stayed inside.
✅ Use a comma before the conjunction when joining two independent clauses.

🔸 SUBORDINATING CONJUNCTIONS
Used to connect a dependent clause to an independent clause.
Type    Examples    Example Sentence
Time    when, after, before, until, while    I’ll call you when I arrive.
Cause/Reason    because, since, as    She left early because she felt sick.
Contrast    although, though, even though    Although it was raining, we went outside.
Condition    if, unless, in case    If it’s sunny, we’ll go to the beach.
Purpose    so that, in order that    He studies hard so that he can pass the exam.
✅ The dependent clause may come before or after the main clause.
→ Although it was late, they continued working.
→ They continued working although it was late.

🔹 PUNCTUATION TIPS
Clause Order    Rule
Dependent clause first    Add a comma: If it rains, we’ll stay home.
Independent clause first    No comma: We’ll stay home if it rains.
Two independent clauses (FANBOYS)    Use a comma before the conjunction

🔸 COMBINING SENTENCES: EXAMPLES
Type    Example
Coordinating    I like tea, but I prefer coffee.
Subordinating    Because I was tired, I went to bed early.
Mixed    I wanted to go out, but since it was late, I stayed home.

❗ COMMON MISTAKES
Mistake    Correction    Why?
She is tired but she go out.    She is tired, but she goes out.    Verb agreement and comma usage
Because it was raining. I stayed in.    Because it was raining, I stayed in.    Fragments must be joined properly
We went home and because it was late.    We went home because it was late.    No need for “and” before subordinating conjunction

💬 EXAMPLE DIALOG
Amy: Did you go to the party?
Leo: No, I was too tired, and I had work early.
Amy: That’s fair. I went, but I left early because it was loud.
Leo: If I had known, I might have come for a bit.
Amy: Maybe next time—unless you’re too busy again!

18.3 RELATIVE CLAUSES: WHO, WHICH, THAT, WHERE
Objective:
To learn how to use relative clauses to give extra information about a noun using relative pronouns such as who, which, that, where, and to distinguish between defining and non-defining clauses.

🔹 WHAT IS A RELATIVE CLAUSE?
A relative clause is a dependent clause that describes a noun. It usually comes immediately after the noun and begins with a relative pronoun.

🔸 COMMON RELATIVE PRONOUNS
Pronoun    Refers To    Example
who    people    The woman who lives next door is a doctor.
which    things or animals    I bought a phone which has a great camera.
that    people or things    The book that I borrowed is excellent.
where    places    This is the café where we met.
whose    possession    He’s the man whose car was stolen.
✅ Use that instead of who/which in defining clauses (especially in informal English).
✅ Do not use a comma in defining clauses.

🔹 DEFINING VS. NON-DEFINING RELATIVE CLAUSES
Type    Explanation    Example
Defining    Gives essential information    The girl who called you is my cousin.
Non-defining    Gives extra (non-essential) info    My cousin, who called you earlier, is a nurse.
✅ Non-defining clauses use commas and never use "that"

🔸 RELATIVE CLAUSES IN USE
Sentence with Clause    Meaning
The teacher who taught me English was kind.    Identifies which teacher
The laptop which I bought last week is broken.    Identifies the specific laptop
Paris, where I studied French, is beautiful.    Adds extra detail about Paris
The man whose car broke down called a tow truck.    Shows possession

🧠 RELATIVE CLAUSE PATTERNS
noun + who/which/that + verb → The man who called is outside.
noun + whose + noun + verb → The student whose phone rang was embarrassed.
noun + where + clause → This is the house where I grew up.

❗ COMMON MISTAKES
Mistake    Correction    Why?
The woman which lives here is nice.    The woman who lives here is nice.    Use “who” for people
The school that I went is far.    The school that I went to is far.    Preposition needed
My brother, that lives in Spain…    My brother, who lives in Spain…    Non-defining → use “who,” not “that”
The place where I met him in…    The place where I met him.    Don’t repeat the preposition

💬 EXAMPLE DIALOG
Tina: Who was that guy who spoke at the meeting?
Marco: That’s James, the consultant whose report we used last year.
Tina: Oh, I remember. He’s the one that gave the presentation on analytics.
Marco: Exactly! He’s working with the team that developed the new app.

18.4 ADVERBIAL CLAUSES OF TIME, REASON, CONTRAST
Objective:
To learn how to use adverbial clauses to express time, reason, and contrast, improving sentence complexity and clarity in both speech and writing.

🔹 WHAT IS AN ADVERBIAL CLAUSE?
An adverbial clause is a dependent clause that modifies a verb, adjective, or entire sentence by giving information about when, why, or how something happens.
It usually begins with a subordinating conjunction (e.g., when, because, although).

🔸 1. CLAUSES OF TIME
Subordinators    Examples
when, while, as soon as, after, before, until    
I’ll call you when I get home.    
We waited until the rain stopped.    
He started cooking after she arrived.    
✅ Used to indicate when something happens.

🔹 2. CLAUSES OF REASON/CAUSE
Subordinators    Examples
because, since, as    
She left early because she was tired.    
Since you’re here, let’s start.    
As it was raining, we stayed indoors.    
✅ Explain why something happens.

🔸 3. CLAUSES OF CONTRAST (CONCESSION)
Subordinators    Examples
although, though, even though, while, whereas    
Although he was tired, he kept working.    
Even though they lost, they played well.    
While she enjoys hiking, he prefers swimming.    
✅ Used to show contrast or unexpected results.

🔹 WORD ORDER AND PUNCTUATION
Clause First    Comma Needed
Although it rained, we stayed.    ✅
We stayed although it rained.    ❌
✅ If the adverbial clause comes first, use a comma before the main clause.

🧠 SENTENCE PATTERNS
Main clause + time/reason/contrast clause
→ I went out because I needed fresh air.
Time/reason/contrast clause + , + main clause
→ Because I needed fresh air, I went out.

❗ COMMON MISTAKES
Mistake    Correction    Why?
I’ll call when I will arrive.    I’ll call when I arrive.    Present tense after “when”
Because was raining, we stayed in.    Because it was raining, we stayed in.    Subject missing
Although he tired, he finished.    Although he was tired, he finished.    Missing verb in the clause
She stayed home since she was sick.    ✔ Correct    “Since” = reason

💬 EXAMPLE DIALOG
Elisa: Why didn’t you come to the event?
Mark: Because I was finishing a report.
Elisa: Oh, I see. I left early since I had a headache.
Mark: I would have come even though I was tired, but the deadline was today.
Elisa: Hopefully next time, we’ll both be free when it happens.

18.5 GERUNDS AND INFINITIVES
Objective:
To understand when to use gerunds (verb + -ing) and infinitives (to + base verb) after common verbs, expressions, and prepositions in English.

🔹 WHAT ARE GERUNDS AND INFINITIVES?
•    Gerund: the -ing form of a verb that functions as a noun
→ Swimming is fun. / She enjoys reading.
•    Infinitive: the base form of a verb with to
→ to swim, to read
→ He wants to leave.

🔸 COMMON VERBS FOLLOWED BY A GERUND (✓ + -ING)
Verb Examples    Example Sentences
enjoy, avoid, suggest, recommend, finish, mind, keep, consider    
She enjoys cooking.    
He avoided answering the question.    
I don’t mind working late.    
✅ These verbs are typically followed by verb + -ing

🔹 COMMON VERBS FOLLOWED BY AN INFINITIVE (✓ + TO)
Verb Examples    Example Sentences
want, need, hope, decide, learn, offer, agree, plan, promise    
I want to leave now.    
We decided to take the train.    
She promised to call later.    
✅ These verbs are followed by to + base verb

🔸 VERBS FOLLOWED BY EITHER (BUT WITH A CHANGE IN MEANING)
Verb    Gerund Meaning    Infinitive Meaning
remember    I remember meeting her. (memory of the past)    Remember to call her. (future reminder)
stop    He stopped smoking. (quit the habit)    He stopped to smoke. (stopped another action in order to smoke)
try    Try restarting the app. (experiment)    Try to restart the app. (make an effort)

🔹 AFTER PREPOSITIONS → USE A GERUND
Preposition Phrase    Example
before, after, without, by, in    
Before going out, call me.    
She left without saying goodbye.    
By working hard, you’ll succeed.    
✅ Never use an infinitive after a preposition

🔸 COMMON EXPRESSIONS FOLLOWED BY INFINITIVES
Expression    Example
be + adjective + to    It’s hard to understand him.
too + adjective + to    It’s too late to call now.
enough + adjective + to    She’s old enough to drive.

🧠 QUICK SUMMARY
Use    Form
As subject    Swimming is fun. (gerund)
After certain verbs    I want to go. / I enjoy going.
After prepositions    She’s good at drawing. (gerund)
After adjectives    It’s important to study. (infinitive)

❗ COMMON MISTAKES
Mistake    Correction    Why?
I enjoy to cook.    I enjoy cooking.    “Enjoy” is followed by gerund
She avoided to answer.    She avoided answering.    Same as above
He suggested me to try again.    He suggested trying again.    “Suggest” not followed by “to”
We’re interested to learn.    We’re interested in learning.    Preposition “in” → use gerund

💬 EXAMPLE DIALOG
Jade: I want to start learning French.
Tom: That’s great! I tried learning it once, but I stopped.
Jade: Why?
Tom: I couldn’t keep practicing regularly. But I recommend taking an online course.
Jade: Thanks! I’m considering doing that. It sounds fun.

18.6 EXPRESSING PURPOSE AND RESULT
Objective:
To learn how to use various structures to express purpose (why something is done) and result (what happens because of something) using connectors like to, so that, in order to, so, and such…that.

🔹 EXPRESSING PURPOSE
Structure    Example
to + base verb    She studies hard to pass the exam.
in order to + base verb    He left early in order to catch the train.
so that + subject + verb    I’m explaining it clearly so that everyone understands.
for + noun / pronoun    This button is for opening the door.
✅ Use “to” and “in order to” with verbs
✅ Use “so that” when the subject of the purpose is different

🔸 PURPOSE: SUMMARY OF PATTERNS
Purpose Clause Form    When to Use    Example
to + verb    Most common, informal/formal    He works to support his family.
in order to + verb    Slightly more formal    They studied in order to pass.
so that + clause    When the subject is different    He explained it slowly so that I could understand.
for + noun/pronoun    To describe function or recipient    This tool is for cutting wood.

🔹 EXPRESSING RESULT
Structure    Example
so + adjective/adverb + that    He was so tired that he fell asleep instantly.
such + (adjective) + noun + that    It was such a cold day that we stayed inside.
as a result    He missed the bus. As a result, he was late.
therefore / thus (formal)    The company lost money. Therefore, they closed two stores.
✅ Use so/that and such/that to show cause and effect
✅ Use as a result, therefore, or thus for more formal written English

🔸 RESULT: SUMMARY OF PATTERNS
Result Structure    Example
so + adjective/adverb + that    She’s so smart that she finished in 10 minutes.
such + (adjective) + noun + that    It was such a mess that we left immediately.
as a result    The project failed. As a result, we lost funding.
therefore / thus    Sales dropped. Therefore, they restructured.

🧠 COMMON MISTAKE PATTERNS
Mistake    Correction    Why?
He works hard so he buy a car.    He works hard so that he can buy a car.    “so that” + subject + verb
It was so nice weather.    It was such nice weather.    Use “such” before a noun
She run to catch the bus.    She ran in order to catch the bus.    Tense and purpose structure
He speaks loudly to everyone hears.    He speaks loudly so that everyone hears.    “so that” for clarity of subject

💬 EXAMPLE DIALOG
Eric: Why are you leaving so early?
Lina: I want to get a good seat, so I’m heading out now.
Eric: Makes sense.
Lina: The last time I went late, it was such a long line that I missed the opening.
Eric: Wow. I’ll leave early too, in order to avoid the crowd.

18.7 LINKING DEVICES FOR FORMAL AND INFORMAL CONTEXTS
Objective:
To identify and use a variety of linking devices (also called discourse markers or connectors) to improve cohesion and coherence in both formal and informal English, adapting to the tone and purpose of the message.

🔹 WHAT ARE LINKING DEVICES?
Linking devices are words or phrases that connect ideas, sentences, or paragraphs. They help organize thoughts, show relationships, and guide the reader or listener through the message clearly.

🔸 TYPES OF LINKING DEVICES AND THEIR FUNCTIONS
Function    Examples (Informal)    Examples (Formal)
Addition    and, also, plus    moreover, furthermore, in addition
Contrast    but, though, while    however, nevertheless, on the other hand
Cause/Reason    because, so    due to, since, as a result of
Result/Consequence    so, then    therefore, thus, consequently
Example/Illustration    like, such as    for example, for instance
Emphasis    really, a lot, actually    in fact, indeed, notably
Sequencing    then, after that, first    firstly, subsequently, in conclusion
Comparison    just like, same as    similarly, likewise

🔹 FORMAL VS. INFORMAL USE
Informal Context    Formal Equivalent
She was late, so we left without her.    She was late; therefore, we left without her.
I think it’s a good idea.    In my opinion, this is a viable proposal.
It was hard, but I did it.    It was challenging; however, I completed it.
I want to do it because it’s fun.    I intend to do it as it is enjoyable.
✅ In speaking and casual writing, informal connectors are acceptable.
✅ In essays, reports, academic/professional writing, use formal alternatives.

🔸 PUNCTUATION AND STYLE TIPS
•    Formal connectors often start new sentences or follow semicolons
→ The results were inconclusive; therefore, the test was repeated.
Informal connectors are frequently used in the middle of sentences
→ It was raining, but we still went outside.
Avoid using too many connectors in a single sentence—keep flow natural

🔹 TRANSITION WORDS BY TONE AND REGISTER
INFORMAL (spoken, casual messages):
so, then, well, but, because, also, anyway, like
NEUTRAL (emails, general writing):
however, for example, even though, in the end
FORMAL (academic/professional writing):
in contrast, in conclusion, furthermore, nonetheless, hence

🧠 PRACTICE STRATEGY
Read an informal paragraph and rewrite it using formal connectors
Group linking words by function and tone
Practice reading aloud with attention to where pauses or emphasis are required

❗ COMMON MISTAKES
Mistake    Correction    Why?
He didn’t study, so therefore he failed.    He didn’t study; therefore, he failed.    Don’t use “so” and “therefore” together
In the other hand    On the other hand    Incorrect preposition
Despite of the problem…    Despite the problem… / In spite of the problem…    “Despite” is not followed by “of”
Also he was tired.    He was also tired. / Moreover, he was tired.    Word order

💬 EXAMPLE DIALOG
Lily: I wasn’t sure what to write, so I just made something up.
Chris: Fair enough. In a formal report, though, you might say “Therefore, a provisional estimate was submitted.”
Lily: Yeah, I should probably switch “so” to “thus” or something.
Chris: Exactly. And instead of “but,” try “however” or “nevertheless.”
Lily: Got it. I guess using the right connector makes your writing sound more serious.
Chris: Absolutely. It improves clarity too.

18.8 IMPROVING FLUENCY WITH SENTENCE VARIETY
Objective:
To develop natural-sounding English fluency by using a range of sentence structures, including simple, compound, complex, and mixed forms, while mastering rhythm, emphasis, and style in both writing and speaking.

🔹 WHY SENTENCE VARIETY MATTERS
Using only one type of sentence (e.g., short simple ones) can make speech or writing sound monotonous or childish. Variety:
Engages the reader or listener
Emphasizes key points
Enhances expression and tone
Helps structure arguments or narratives clearly

🔸 TYPES OF SENTENCE STRUCTURES FOR FLUENCY
Type    Description    Example
Simple    One independent clause    She loves music.
Compound    Two independent clauses (FANBOYS)    He cooked dinner, and she set the table.
Complex    Independent + dependent clause    Although it was late, they kept working.
Compound-Complex    Two or more independent + one or more dependent    She was tired, but she stayed because the topic was interesting.

🔹 TECHNIQUES TO IMPROVE FLUENCY THROUGH STRUCTURE
1.    Use transitions to connect ideas smoothly
→ First, we analyzed the results. Then, we compared them.
2.    Alternate sentence length
→ The room was silent. Everyone was watching. Then, suddenly, she spoke.
3.    Start with a dependent clause
→ While I agree with your point, I believe we need more evidence.
4.    Use participle and reduced clauses
→ Knowing the risks, he went ahead. / Given the circumstances, we adapted quickly.
5.    Insert modifiers for emphasis or clarification
→ The report, surprisingly, showed no errors.
→ She, unlike the others, volunteered immediately.

🔸 COMMON PATTERNS FOR STYLE AND FLOW
Purpose    Structure Pattern    Example
Emphasis    Intro phrase + comma    To be honest, I didn’t enjoy it.
Cause & Effect    Clause + because/since/as    He left early because he felt unwell.
Contrast    Clause + although / even though / however    The task was difficult, but we completed it.
Conditions    If/unless clause + main clause    If you’re ready, let’s begin.
Comparison    Clause + just as / like / similarly    She dances just as well as her sister.

🔹 IMPROVING FLUENCY IN SPEAKING
•    Pause and stress naturally: vary rhythm using intonation
•    Chunk ideas: group words that belong together
→ “Even though it was raining // we still went outside.”
•    Use discourse markers: Actually, By the way, In that case, So anyway…
•    Practice with varied sentence starters:
It seems that…
From what I understand…
To put it another way…

❗ COMMON MISTAKES
Mistake    Correction    Why?
I like it. Because it’s easy.    I like it because it’s easy.    Avoid sentence fragments
Although she was tired. She continued.    Although she was tired, she continued.    Subordinating clauses need a main clause
The movie was good, and because it was short.    The movie was good because it was short.    Don’t mix conjunction types incorrectly
He work fast he finish early.    He works fast, so he finishes early.    Missing connectors and verb agreement

💬 EXAMPLE DIALOG
Amy: How do you make your presentations flow so well?
Liam: I try to mix short and long sentences. It helps with rhythm.
Amy: Yeah, I tend to just list facts.
Liam: Try using transitions. Like: “To begin with…”, “More importantly…” It helps guide the audience.
Amy: I’ll work on that. Also, starting with a question might catch attention.
Liam: Exactly. And ending with a strong statement keeps it memorable.

18.9 UNIT 18 REVIEW
Objective:
To consolidate all skills related to complex sentence structures, linking ideas, and fluency techniques, ensuring learners can communicate with greater clarity, precision, and coherence in both speech and writing.

📘 WHAT YOU LEARNED IN THIS UNIT
🔹 SENTENCE TYPES AND STRUCTURE
•    Simple sentences: one clause → I like music.
•    Compound sentences: two independent clauses → She sings, and he plays guitar.
•    Complex sentences: independent + dependent clause → Because it was raining, we stayed inside.
•    Compound-complex sentences: multiple independent and dependent clauses combined

🔹 COORDINATING AND SUBORDINATING CONJUNCTIONS
Coordinating (FANBOYS): for, and, nor, but, or, yet, so
Subordinating: because, although, while, since, if, when, after…

🔹 RELATIVE CLAUSES
who, which, that, where, whose
Defining vs. non-defining → The man who called you is here. / My car, which I bought last year, is electric.

🔹 ADVERBIAL CLAUSES
Of time: after, when, while
Of reason: because, since
Of contrast: although, even though, whereas

🔹 GERUNDS AND INFINITIVES
Gerund after certain verbs: enjoy, avoid, suggest → I enjoy swimming.
Infinitive after others: want, decide, promise → She wants to leave.
Differences in meaning: stop to eat vs. stop eating

🔹 PURPOSE AND RESULT
Purpose: to, in order to, so that
Result: so...that, such...that, therefore, as a result

🔹 LINKING DEVICES FOR TONE
Informal: so, but, and, like, because
Formal: however, therefore, in addition, as a result, nevertheless

🔹 SENTENCE VARIETY AND FLUENCY
Combining sentence types to avoid monotony
Using transitions for flow: Meanwhile, Eventually, On the other hand
Techniques like inversion, reduced clauses, participle phrases for advanced fluency

🔹 LISTENING AND SPEAKING PRACTICE
Recognizing and using complex structures in natural speech
Practicing storytelling, summarizing, and elaborating with fluency
Focus on relative clauses, subordinators, discourse markers, and intonation

💬 EXAMPLE DIALOG
Clara: You’ve really improved your speaking. Your ideas flow so smoothly now.
David: Thanks! I’ve been working on using more complex sentences—like starting with although or adding relative clauses.
Clara: It shows. And your transitions are great. I noticed you said, “However, we should also consider…” in the meeting.
David: Yeah, I’m trying to sound more natural and professional at the same time.
Clara: Keep it up. Variety makes a big difference.