Sentences

English written communication is made up of a series of sentences. However, these sentences must be grammatically complete to communicate meaning effectively.

Introduction

Sentences seem straightforward (a capital letter and a full stop plus everything in between), but there are fundamental rules which govern the ways they can be constructed.

If these rules are broken (and they often are), the results are at best distracting, and at worst incomprehensible.

Sentence Fundamentals

Let's consider why some sentences "work" and others don't.

Try reading the following examples out loud.

Hmmm.

Only one of these examples is correct. As in, only one is a complete sentence.

Can you tell which one?

Dramatic music

The answer is The dog slept.⁠—but why is this the case?

Let's reconfirm the definition of a sentence.

So, a sentence must express a complete thought. If it does not, the reader will wonder about whatever remains unresolved.

In addition, a sentence must refer to an action or condition. This means we need a subject and a related verb.

Returning to the examples above, the sentence The dog slept is correct because it contains a subject (The dog) and a related verb (slept). Thus, it expresses a complete thought.

Let's revisit the two incorrect examples to determine what is wrong with them.

In the first example, we have a subject (Andrew) and a verb (waited); however, the sentence does not express a complete thought because we do not know who or what Andrew is waiting for.

In the second example, we have a verb (visited) and an object (the farm), but no subject that is initiating the action.

Let's see if we can complete each of these sentences.

That's better: each sentence now has a subject and a related verb; thus, each sentence expresses a complete thought.

When forming sentences, we must take the time to make sure they are grammatically correct.

If a sentence does not include a subject and a related verb, or it does not express a complete thought, it is incorrect. This results in a distracting and unsatisfying experience for the reader.

Clauses

All sentences (with the exception of imperative sentences) are made up of at least one clause.

A single clause can form a sentence, or a sentence can be constructed from multiple clauses.

However, we must make sure that each clause within a sentence is complete (i.e. that it contains a subject and a verb), and that multiple clauses are correctly linked by an appropriate conjunction.

There are two kinds of clauses in English: independent clauses and dependent clauses.

Independent Clauses

Like all clauses, an independent clause must have a subject and a related verb. However, as the name suggests, an independent clause can exist independently, and thus can form a sentence by itself.

So, an independent clause can form a sentence by itself, although it doesn't have to.

Consider the following example.

Here we have a subject (Dwayne) with a related verb (slept). Thus, we have a clause.

In addition, because this clause expresses a complete thought it can form a sentence by itself. Thus, it is an independent clause.

Let's see if we can expand this example a little by adding an object.

Is this example still an independent clause?

Yes, this sentence expresses a complete thought and can function as a sentence; thus, it is still an independent clause.

Okay, let's try adding another word:

Hmmm.

Something is different

The presence of the word As means that this clause is no longer independent because it now depends on something else to form a complete thought. Thus, it is a dependent clause.

Dependent Clauses

A dependent clause must contain a subject and a verb; however, it cannot form a complete sentence by itself due to the presence of a dependent marker word.

Let's see if we can create a complete sentence which contains our dependent clause.

Is this a grammatically complete sentence?

Yes, it is.

Our dependent clause (As Dwayne slept in his bunk) is connected by the coordinating conjunction as to an independent clause (Ellen fought the monster). Thus, this sentence now expresses a complete thought.

Sentence Types

In English, there are four common sentence types: simple, compound, complex and compound-complex.

These sentence types are categorised according to the number of independent or dependent clauses they contain.

Simple sentences

Simple sentences contain one independent clause and no dependent clauses.

Simple sentences can, however, contain conjunctions.

While it is tempting to place a comma before the conjunction in a simple sentence, this is not needed.

Compound sentences

Compound sentences contain two or more independent clauses linked by coordinating conjunctions.

In compound sentences we do place a comma before the coordinating conjunction.

Complex sentences

Complex sentences contain one independent clause and one or more dependent clauses.

If a dependent clause comes before the independent clause, a comma should separate the two.

If a dependent clause comes after an independent clause, no comma is required.

Compound-complex sentences

Compound-complex sentences contain two or more independent clauses and at least one dependent clause.

If a sentence begins with a dependent clause that applies to two independent clauses that follow, we should insert a comma after the dependent clause, but not between the two independent clauses

If a dependent clause occurs between two independent clauses and applies only to the second, we should place a comma before and after the dependent clause.

Phrases

A note on phrases.

When we refer to a noun or a verb with regards to grammar, we are really referring to a noun phrase or a verb phrase.

Thus, when we say that a sentence is composed of one or more clauses, and a clause must contain a noun and a verb, we really mean that a clause must contain a noun phrase and a verb phrase.

Consider the following example.

Here we have a noun phrase (A disorganised person) and a verb phrase (is always underprepared). Together, they form an independent clause that acts as a complete sentence.

This concept extends to adjectives and adverbs, which together with their related words should be thought of as adjective phrases and adverb phrases.

This is also true of prepositional phrases, although they should be considered adjectives or adverbs depending on the type of phrase they govern.

This is not something we need to think about in our day to day writing; however, if we find that our sentences don't "sound" right, we can always break them down into their respective phrases to make sure everything fits together the way it should.

Active and Passive Voice

We can make a stylistic choice to write our sentences in the active voice or passive voice depending on whether we want to draw the reader's actions to the subject or the object of the sentence.

Consider the following examples:

In the first example, the subject (He) is the focus of the sentence. By contrast, in the second example the object (Dinner) is the focus of the sentence.

In general, we should write our sentences in the active voice because this more closely mimics English speech. (We usually establish who or what is doing something before referring to whatever it is they are doing.)

However, there are cases in which the passive voice is preferred.

For example, in the scientific world the results of an experiment are more important than the people who carried it out.

In addition, we can use the passive voice if we do not want to draw attention to a subject. This could be because the subject is humble, or because we want to avoid casting blame.

Imperative Sentences

An imperative sentence is an exception to everything we have said about grammatically complete sentences.

This is because an imperative sentence does not require a subject to be grammatically complete. Instead, it needs only a strong verb that is being expressed as a command from an unspecified subject to an unspecified object.

Consider the following examples.

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