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Sentence building

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English has two basic ways of combining words into groups: phrases and clauses.

  • Phrases are centred around nouns (in the van, by early morning).
  • Clauses are centred around verbs (she runs the marathon; when he saw the ruins).
Types of clausesCombining clauses

Types of clauses

All sentences are constructed from two types of clauses.

  1. The main, principal, or independent clause. It contains a subject (noun), a predicate (verb), and expresses a complete thought:

She decided to walk to the park.

(subject)          (verb)              (= complete thought)

  1. The subordinate or dependent It also contains a subject and a verb but does not express a complete thought. Subordinate clauses often begin with words like since, while, although, despite, etc.:

Because it was a sunny day

(subject)           (verb)              (= incomplete thought)

Combining clauses

Combining a subordinate and a main clause

Combining clauses is what sentence building is all about. Joining a subordinate clause with a main clause requires only a comma:

Because it was a sunny day, she decided to walk to the park.

(subordinate)                           (main)

Combining two main clauses

The tricky part comes when two main clauses are joined together. Punctuation options include:

A period: It was a sunny day. She decided to walk to the park.

A semi-colon: It was a sunny day; she decided to walk to the park.

A comma with a linking word (coordinating conjunction): It was a sunny day, so she decided walk to the park.

Other coordinating conjunctions are and, but, yet, or, nor and for.

✘ Comma splices: Do not use a comma to join two main clauses in a sentence: e.g., It was a sunny day, she decided walk to the park. A comma is too weak a form of punctuation, and the resulting error is called a comma splice.

✘ Run-on sentence: Joining two main clauses with no punctuation is called a run-on sentence.

Both are considered to be major sentence errors.

A special case is when two main clauses are combined, and the second one begins with however (or other conjunctive adverbs like therefore, thus or nevertheless). A semi-colon must be used; a comma is too weak, and will create a comma splice:

It was raining; however, she decided to walk to the park.