Compound Sentences and Complex Sentences

In the English language, sentence construction is quite imperative to understanding. A sentence can be a sequence, set or conglomerate of words that is complete in itself as it typically contains a subject, verb, object and predicate. However, this sentence regardless of its intent, would be chaotic if not constructed properly. Proper sentence construction helps in conveying the meaning or intent of the sentence and because reading and writing constitute the two major activities in communication, knowledge on sentence construction will directly apply to how you speak, write and communicate. Hence, it contributes to your proficiency in English.

Now, in grammar, there are several ways a sentence can be constructed. This is called ‘Sentence Composition’. It is the grouping of sentences concerning the number and the type of clauses embedded in their syntactic structure. Based on this analogy, there are different kinds of sentences but what distinguishes one from the other is the type, number of clauses used and the synergy of both. Hence, we cannot identify Compound and Complex sentences without examining the typology of clauses. This is because this typology will succinctly reveal the patterns required for the construction of either type of sentences.

Types of clauses

All types of clauses

Writing is one of the most utilized means of communication. A text, letter, email, or comment on one’s social media are all the means we integrate writing on a daily. Writing is somewhat one of the strongest communication means. However, with writing, especially when the words aren’t used in their correct syntax, with the right punctuation or follow their intended pattern, there’s often a misinterpretation.

One way to prevent your written words from being misconstrued is by understanding and applying the different types of clauses correctly. In the context of the English language, a clause isn’t a condition. No, a sentence clause is a group of related words that have both a subject and a predicate. Every complete sentence has at least one clause, else it’s termed incomplete or a sentence fragment. There are several types of clauses according to their form or how they’re used in a sentence. Here they are;

Dependent clause

As the name implies, a dependent clause is that which cannot stand alone. It relies on another clause for completion and meaning. A dependent clause is quite easy to identify in a sentence as it usually begins with subordinating conjunctions like; because, although, where, after, once, etc. You might notice that the conjunction ‘but’ isn’t in the mix. This is because ‘but’ is a coordinating conjunction.

With three types of conjunction, (Coordinating, subordinating or correlative) which the dependent clause uses, appends a subordinate clause to the main clause. This is known as subordinating or subordinate conjunction and it is a word or a phrase that highlights the relationship between ideas. Such conjunctions represent the concept of time, contrast, cause and effect. Dependent clauses cannot make meaning on their own, here’s how.

‘Because I was alone’

‘Although she won’

‘After mike left’

These are all sentences, however, they do not make meaning. No one knows what happened after she won or after Mike left, hence the message behind the sentence isn’t conveyed.

Types of dependent clauses

Dependent clauses come in different types, each satisfying a particular function within a sentence. Here are the types of dependent clauses which are worth mentioning;

  • Relative clause
  • Noun clause
  • Adverbial clause

Relative clause

A relative clause is an adjectival clause. In essence, it describes the noun or pronoun in the sentence. Being a subset of a dependent clause, they do not make meaning alone and relative clauses can be identified by three pointers. First, a subject and a verb as a relative clause will depict the action and its doer. Next, you can identify a relative clause by its relative pronoun/adverb like who, whom, which, where, why, when, etc., and finally by its adjective as it usually answers questions about the noun.

A relative clause can be written in several ways as the relative pronoun can be written before the predicate as in ‘When we get to the bar’. It can also be written with the relative pronoun as the subject as in ‘Who came in?’ These clauses describe a noun and sometimes they are intricate to the message to be conveyed while other times they’re an extra detail that can be lived without.

Noun Clause

As the name implies, a noun clause is that which takes up the function of a noun. A noun clause can depict the subject, object or a complement. However, it is still a dependent clause as it cannot depict meaning alone. Similar to the relative clause, a noun clause mostly begins with a relative pronoun. However, a subordinate conjunction can also begin a noun clause. For example, ‘What I ate is giving me a tummy ache’.

Adverbial clause

An adverbial clause functions as an adverb. Hence it is that type of dependent clause that modifies or describes a verb, adjective or another adverb in a sentence. This clause sub-type also contains a subject and a predicate as it mostly begins with a subordinating conjunction. An adverbial clause depicts time, condition, place, contrast purpose or result. Here’s a typical example of an adverbial clause in a sentence.

‘Although the world is full of suffering, it is also full of the overcoming of it.” – Keller 1903. The underlined sentence is the adverbial clause as not only does it begin with the subordinating conjunction ‘although’, it cannot make meaning on its own as it’s only a fragment of a sentence.  This is why dependent clauses of all types are combined with an independent clause, which brings us to the next type of clause,

Independent clause

Contrary to the dependent clause, an independent clause is that which can stand on its own and convey a complete message or thought. An independent clause is a complete sentence as it has the subject, the verb and most times an object. It’s a simple sentence. For example, if one were to write ‘Mike bought a book’. The sentence is complete because there is a subject, Mike, a verb, bought and an object, which is the book. However, in the subject of English, although independent clauses make perfect meaning on their own, they can be appended to other clauses for more complexity or depth.

An independent clause is joined to another clause through the use of semicolons, commas, or coordinating conjunctions like but, and, or, nor, yet, etc. to form a different type of sentence, known as the complex sentence. This brings us to the second part of this piece.

Structural types of Sentences

Before we can highlight the structural sentence types, we have to acknowledge the use of conjunctions in these sentence types.


Conjunctions refer to the connecting words or phrases that are used to combine different clauses or phrases to highlight a deeper meaning of the sentence. They are conjoining words that string together most independent and dependent clauses. Now, there are different types of conjunctions and plays out a different function. However, for the sake of the premise, here are the conjunctions that are most applicable to the topic;

Coordinating conjunctions: A coordinating conjunction’s function is to join words, clauses or phrases that possess similar grammatical structure. They connect main clauses to each other and short phrases too. Coordinating conjunctions are seven in number and they are easily identified with the acronym FANBOYS which as previously stated stands for For, And, Nor, But, Or, Yet and So. Coordinating conjunctions are mostly used in a compound and compound-complex sentences – more on this soon.

Subordinating conjunctions: This conjunction type is used to introduce a subordinate clause. Subordinate conjunctions also join an independent or subordinate clause to the main clause. In essence, the union between a main clause and a subordinate clause is made possible with subordinating conjunctions. They are many but they include; although, because, before, if, how, since, till, until, whenever, whether, as soon as, even if, and many others. Such conjunctions are often called ‘ a heart word’ because they merge two sentences.

Correlative conjunctions: These are simply paired words. Correlative conjunctions join words, phrases or clauses which have a complementary relationship. They are used to show the relationship between two or more things, thoughts, feelings or concepts. They include; either/or, neither/nor, whether/or, not only/but also and finally, both/and.

With knowledge of the distinct types of sentence clauses and conjunctions, this next step should be a breeze. This is because to fabricate the different types of sentences, different types of clauses are needed. First off, a sentence is the largest divisible unit of any language and concerning English, it begins with a capital letter and truncates with a type of punctuation, either a period, a question mark or an exclamation mark.

Here is an overview of the types of sentences.

Simple sentence

A simple sentence possesses an independent clause of any sub-class. A simple sentence has nothing to do with a dependent clause as it satisfies a complete thought and has meaning. A simple sentence can be very short like ‘I run’ and it can also be moderately lengthy and feature conjunctions like ‘and’. Example; ‘A simple sentence has a subject and a predicate’. This type of sentence can have more than one subject, verb and object. Example; ‘Serah and Joey arranged the entire house’. Simple sentences are often featured as slogans for brands. A common example is Nike’s Just do it or Skittles’ Taste the Rainbow.

Compound sentence

Compound sentences are sentences that possess at least two independent clauses joined together by a coordinating conjunction or punctuation. This type of sentence doesn’t require a dependent clause and all the independent clauses in a compound sentence are of equal importance. Example; ‘Mike cooked and Serah cleaned’. Typically ‘Mike cooked’ is a simple sentence that conveys meaning on its own, likewise is ‘Serah cleaned’. However, together through the coordinating conjunction ‘and’ which reveals a simple relationship between them, both sentences reveal more depth and meaning when added together. Other examples of compound sentences include;

  • Either I accept your offer or I decline it; these are the two options I have.
  • The journey had only begun but I was already exhausted.
  • I came as fast as I could but I was too late.
  • The birds were chirping, I was happy.

Compound sentences feature coordinating conjunctions and they’re seven of these conjunctions which can be abbreviated as FANBOYS which stands for For, And, Nor, But, Or, Yet, and So. Coordinating conjunctions aren’t the only means of joining independent clauses in a compound sentence. These clauses can also be joined by commas (,), semicolons (;), and semicolons with a transitional expression. The sentence ‘The birds were chirping, I was happy’ depicts how the comma is used to join two main clauses and the first sentence shows how the semicolon is used with a transitional expression.

Complex sentence

Complex sentences are formed from combining one independent clause with a minimum of a subordinate clause. Since the clauses are different, the structural hierarchy of a complex sentence is unequal. Although both clauses express similar or related thoughts, the independent clause will most definitely act as the foundation of the sentence while the dependent clause will append related information. Here’s a depiction;

‘The bug died when it hit the wall’

The independent or stand-alone clause in this sentence is ‘The bug died’. This clause is stand alone because saying ‘The bug died’ makes perfect sense as opposed to its subordinate counterpart ‘when it hit the wall’.

If a person writes or says the subordinate part of the sentence alone, more context would be required and questions like ‘when what hit the wall?’ would follow. But with its independent part, no further information would be required as a simple message is conveyed. Hence, adding the subordinate conjunction ‘when’ increases the complexity of the sentence and also gives it more context, thus creating a complex sentence. It’s important to note that a complex sentence is formed with a subordinating conjunction and other punctuation. Here are more examples of a complex sentence;

  • Although I was mad, she had a way of making me smile.
  • When in doubt, seek Christ.
  • He studied hard because he wanted to get into medical school.

Compound-complex sentence

A compound-complex sentence is a combination of both the compound and the complex sentence. In essence, this sentence type has the features of both. Ideally, a compound-complex sentence is that which has two or more independent clauses like the compound sentence and one or more dependent clauses like the complex sentence added together by a conjunction. Compound-complex sentences are often used in poetry, story writing, articles and literary pieces. For example, here’s an excerpt from a popular book;

‘His blue eyes were light, bright and sparkling behind half-mooned spectacles and his nose was very long and crooked, as though it had been broken at least twice.’ – J.K. Rowling, Harry Potter and the Sorcerer’s Stone.

From this sentence, we can identify two main clauses. The first main clause is ‘His blue eyes were light, bright and sparkling behind half-mooned spectacles’. This descriptive sentence forms the first main clause as it makes a complete meaning on its own. ‘His nose was very long and crooked’ forms the second independent clause. Together both sentences form a compound sentence because as you remember, a compound sentence features two main clauses joined together by a coordinating conjunction such as ‘and’.

Moving on to the subordinate part of the sentence we have ‘As though it had been broken at least twice’. No matter how you spin this sentence, it will always require more context from your receiver which is why it’s appended to two independent clauses. Together the three sentences form a descriptive compound-complex sentence.

The main and subordinate clauses in a compound-complex sentence can be arranged in any manner. The above example features the main clauses first while the subordinate clause is appended at the end. Here’s an example that conveys the previous thought.

Kate doesn’t like sports because they can be brutal so she doesn’t go to the games.

This example seems much simpler than the previous but it still follows the necessary syntax. ‘Favor doesn’t like sports’ forms the first independent clause, ‘because they can be brutal’ is the subordinate clause and finally, ‘she doesn’t go to the games’ is the second independent clause.

Compound-complex sentences are the most complicated of all four types of sentences. This is because they bear the characteristics of the other three.

Compound Vs Complex sentence

The difference between a compound and a complex sentence is in the sentence structure. Here are some ways in which they differ;


A compound sentence takes the form;

Independent clause + Coordinating conjunction + independent clause = Compound sentence while a complex sentence takes the form;

Independent clause + Subordinating Conjunction + Dependent clause +Subordinating Conjunction + Dependent clause = Complex sentence.

Number and type of clauses

 In terms of main clauses, a compound sentence has two or more independent clauses while a complex sentence has just one. Concerning subordinate or dependent clauses, a compound sentence has none while a complex sentence has a minimum of one.

Conjunction types

In a compound sentence, the two main clauses are combined with the use of coordinating conjunctions like for, and, nor, but, or, yet and so (FANBOYS). For a complex sentence, it’s quite different. The main and subordinate clause(s) are combined with subordinating conjunctions like when, if, how, where, until, after, provided that, etc.

Use of conjunctions

In a compound sentence, coordinating conjunctions cannot be used at the beginning of a sentence. It just wouldn’t make sense. For instance ‘So the train was late I took the bus’. You can agree this looks like a poorly written sentence. Hence it makes more meaning as ‘The train was late, so I took the bus’.

In a complex sentence, subordinating conjunctions can be used at the beginning of a sentence like so, ‘When it hit the wall, the bug died’.


Compound and complex sentences also have similarities. Here are a few of them;

  • Both the compound and the complex sentence have a minimum of two clauses.
  • They both have at least one independent clause.
  • The position of the clauses depends on the preference of the writer.


Understanding the structure of a sentence is important when learning English. With this understanding, one can go on to write articles and literary pieces with the proficient use of English. With regard to this, compound and complex sentences, however similar are unique in their form and syntax. While one applies just the independent sentence clause, the other uses both the independent and the subordinate clauses. Knowing how to identify either type and construct them with their distinct conjunction types and clauses will directly translate to the conciseness, engagement and readability of your work.

Compound Sentences and Complex Sentences 1 | Scientific Editing
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By Bizhan Romani

Dr. Bizhan Romani has a PhD in medical virology. When it comes to writing an article about science and research, he is one of our best writers. He is also an expert in blogging about writing styles, proofreading methods, and literature.

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