Once you know the parts of speech, the next step is learning how they combine into sentences. Here is everything you need — from the simplest sentence to the most sophisticated.
A sentence is not just a string of words. It is a structure, and once you understand that structure, you can build sentences of any length or complexity with control.
Every sentence in English, from the shortest command to the longest opening of an academic paragraph, is built from the same ingredients: subjects, predicates, and the ways that clauses combine. This guide starts with those basics and builds up to the structures used in advanced academic and professional writing. It covers subjects and predicates, phrases and clauses, the four sentence structures, the seven basic clause patterns, sentence purposes, word order, active and passive voice, common structural errors, parallelism, relative clauses and techniques for combining sentences with variety. It includes two worked examples, a checklist, common mistakes and ten practice questions.
It follows Parts of Speech and leads into Punctuation Rules. It also supports How to Write a Perfect Paragraph, Transitions & Cohesion and Common Errors in English.
A complete sentence normally does two things: it names something (the subject) and says something about it (the predicate). Without both, a group of words is a fragment, not a sentence.
Birds fly. "Birds" is the subject, "fly" is the predicate.
The tired old dog slept peacefully on the porch all afternoon. The subject is "The tired old dog"; the predicate is everything else.
Two small notes keep this accurate. First, in an imperative sentence such as Close the door, the subject you is understood, not written. Second, in speech and in some styles of writing, short minor sentences such as Thanks. or Not now. are normal. In formal and exam writing, however, aim for full sentences unless you are making a deliberate stylistic choice.
The subject is who or what the sentence is about. It is usually a noun, pronoun or noun phrase.
The predicate tells what the subject does, is, or has done to it. It always contains the main verb.
The verb decides what else the sentence needs. A transitive verb takes an object (She wrote a letter). An intransitive verb does not (She laughed). A linking verb connects the subject to a description (She is happy). Many verbs can be used in more than one way.
Diagram 1. "The exhausted marathon runner collapsed onto the grass and gasped for breath."
This distinction underpins everything that follows. A phrase is a group of related words that does not have its own subject-verb pair. A clause does contain a subject and a verb. Every sentence contains at least one clause.
| Phrase type | Example |
|---|---|
| Noun phrase | the old wooden chair |
| Verb phrase | has been waiting |
| Prepositional phrase | in the morning |
| Adjective phrase | very tired |
| Adverb phrase | quite slowly |
Clauses come in two kinds, and the difference is the most important idea in this guide.
Expresses a complete thought and can stand alone as a sentence: The rain stopped.
Has a subject and a verb but cannot stand alone, because it depends on an independent clause: because the rain stopped (incomplete on its own).
Dependent clauses do three jobs, and each answers a different question:
| Type | Job | Example |
|---|---|---|
| Adverbial clause | Says when, why, how, where or under what condition | We left because it was late. |
| Relative (adjective) clause | Describes a noun | The book that I borrowed is overdue. |
| Noun clause | Acts as a subject or object | I know that she is right. |
Adverbial clauses start with a subordinating conjunction. Choose it by meaning:
| Meaning | Subordinators |
|---|---|
| Time | when, while, after, before, until, as soon as |
| Reason | because, since, as |
| Contrast | although, though, while, whereas |
| Condition | if, unless, provided that |
| Purpose and result | so that, in order that |
Sentences are classified by structure according to how many independent and dependent clauses they contain. These four categories cover all full sentences built from clauses.
Diagram 2. Count the clauses first; then decide the structure.
| Structure | Made of | Example |
|---|---|---|
| Simple | One independent clause | The dog barked. |
| Compound | Two or more independent clauses joined by a coordinating conjunction or semicolon | The dog barked, and the cat ran. |
| Complex | One independent clause plus one or more dependent clauses | Because it was raining, the dog barked. |
| Compound-complex | Two or more independent clauses plus one or more dependent clauses | Because it was raining, the dog barked, and the cat ran inside. |
"Simple" does not mean short. A simple sentence has only one clause, but it can have a compound subject or predicate and long phrases: The exhausted marathon runner collapsed onto the grass and gasped for breath. The coordinating conjunctions are easy to remember with FANBOYS: for, and, nor, but, or, yet, so. For their punctuation, see Transitions & Cohesion.
Under the surface, each clause follows one of a small number of patterns of subject (S), verb (V), object (O), complement (C) and adverbial (A). Grammars by Quirk and his colleagues, widely used in universities, list seven. Some textbooks list five or six, so check your own course book.
| Pattern | Example |
|---|---|
| SV | The baby slept. |
| SVO | She wrote a letter. |
| SVC | The results are significant. |
| SVA | The conference begins on Monday. |
| SVOO | She sent the committee the report. |
| SVOC | The committee appointed her chair. |
| SVOA | He put the keys on the table. |
A complement completes the meaning of a linking verb (The results are significant) or describes an object. An adverbial can be required (begins on Monday) or optional extra information (Sometimes she sings beautifully). Knowing these patterns helps you see why some sentences feel incomplete.
Form and function do not always match. Could you open the window? is an interrogative in form but a polite request in purpose.
Standard English statements follow Subject-Verb-Object order: Maria reads novels. "Novels reads Maria" is not grammatical. This is one of the most common difficulties for learners whose first language places the verb at the end of the sentence, as Urdu, Hindi, Japanese and Turkish do. In English the verb comes early, straight after the subject, so practise saying the "who does what" part first.
English also allows planned variations:
In an active sentence, the subject does the action: The team finished the report. In a passive sentence, the subject receives the action: The report was finished by the team. The doer can be left out altogether: The report was finished.
Active sentences are usually shorter and clearer, so they are a good default. The passive is useful when the doer is unknown or unimportant (The window was broken), when the receiver matters more (The patient was admitted at noon), and in scientific writing that focuses on the process. The weakness of the passive is that it can hide who is responsible.
| Error | Example | Fix |
|---|---|---|
| Fragment | Because I was late. | Attach it: Because I was late, I missed the bus. |
| Run-on | I was late I missed the bus. | Add punctuation or a conjunction. |
| Comma splice | I was late, I missed the bus. | I was late, so I missed the bus. / I was late; I missed the bus. |
| Stringy sentence | I woke up and I ate and I left and I walked and … | Subordinate some ideas and cut "and". |
| Choppy sentences | I was late. I ran. I missed it. | Combine: Because I was late, I ran, but I still missed it. |
A comma splice can be repaired in four ways: a full stop, a semicolon, a comma plus a coordinating conjunction, or by making one clause dependent. See Common Errors in English for more.
Parallelism means keeping grammatically similar elements in the same form, especially in lists and pairs.
| Not parallel | Parallel |
|---|---|
| She likes reading, to write and swimming. | She likes reading, writing and swimming. |
| The plan is cheap, fast and works well. | The plan is cheap, fast and effective. |
| He is not only clever but also works hard. | He is not only clever but also hard-working. |
Pairs such as not only … but also, either … or and both … and must be followed by the same kind of structure on each side.
Relative clauses add detail about a noun using who, whom, whose, which or that, and they come in two forms that change both meaning and punctuation.
The students who studied hard passed the exam. Only those students; the information is essential.
My sister, who lives in Canada, is visiting next month. Extra detail; the sentence works without it.
Use who and whom for people, which for things, and that for things (and often people) in restrictive clauses. In British English, which is also commonly used in restrictive clauses, while many American style guides prefer that; follow the convention of your course.
Accurate sentences are not enough. Good writing varies the length, structure and opening of sentences, so that the rhythm does not become monotonous. One technique is to start with a short sentence and expand it by answering questions: what kind, where, when, why?
Diagram 3. A simple sentence becomes a complex one.
| Technique | Example |
|---|---|
| Subordination | Although the road was icy, we drove on. |
| Coordination | The road was icy, but we drove on. |
| Participle opener | Slipping on the ice, the car slowed down. |
| Appositive (a renaming phrase) | Ali, my oldest friend, lives in Lahore. |
| Varying length | It was dark. The wind rose and the old shutters began to bang against the wall. |
Beware of dangling openers: Slipping on the ice, the car slowed down works only because it is the car that slips. See Common Errors in English for more on modifiers.
Consider this sentence from a news report: "Although the storm had passed by morning, residents remained cautious, and local authorities continued monitoring the river levels closely." It is a compound-complex sentence. The dependent clause "Although the storm had passed by morning" sets the context. The two independent clauses, "residents remained cautious" and "local authorities continued monitoring the river levels closely", are joined by "and". Recognising this structure helps a reader see which idea is background and which are the main facts.
Sentence: "When the bell rang, the students who had finished their tests handed them in, and the teacher thanked everyone."
Try it yourself. Name the structure of: "Although it was late, she kept working."
Sample answer: Complex. "Although it was late" is a dependent clause; "she kept working" is the independent clause. There is one independent and one dependent clause.
Draft: "The market opened. It was crowded. People bought fruit. The sun was hot. Some vendors sold cold drinks."
Revised: "When the market opened, it quickly became crowded with people buying fruit. Because the sun was hot, some vendors sold cold drinks."
What changed. Five short simple sentences became two: a complex sentence and another complex sentence. The relationships (time, reason) are now stated, not left for the reader to guess.
Try it yourself. Combine into one sentence: "The bus was late. We waited. It started to rain."
Sample answer: "While we waited for the late bus, it started to rain." Other correct versions are possible.
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| Mistake | Better habit |
|---|---|
| Thinking "simple" means short | Count clauses, not words |
| Treating a dependent clause as a sentence | Attach it to an independent clause |
| Joining two sentences with only a comma | Use a full stop, semicolon or conjunction |
| Putting the verb at the end of the English sentence | Say the subject, then the verb straight away |
| Using the passive everywhere | Prefer active unless there is a reason |
| Long chains of "and" | Subordinate less important ideas |
| Non-parallel lists | Make each item the same form |
| Commas in the wrong place in relative clauses | No commas for essential information; commas for extra detail |
Sentence structure is the difference between writing that merely communicates and writing that persuades, flows and holds a reader's attention. Once parts of speech (Topic I) tell you what each word does, sentence structure tells you how to arrange those words into clear, correct and increasingly sophisticated ideas, which is the foundation for the rest of this Grammar Basics series. Continue with Punctuation Rules.
Activity: give students a long sentence from a text they are reading and ask them to find each verb, mark each clause, name the structure and identify the pattern of the main clause. Then ask them to rewrite it as three shorter sentences and decide which version reads better.
Please note: grammar books differ in how many clause patterns they list (five to seven) and in some terms, so follow your own syllabus. The examples are original and chosen for clarity.
10 questions. Select an answer for each, then submit to see your score instantly.