The Grammar Rules for Clauses in English
1. A clause is a group of words that contains both a subject and a predicate but cannot always be considered as a full grammatical sentence. Clauses can be either independent clauses (also called main clauses) or dependent clauses (also called subordinate clauses).
2. An independent clause (or main clause) contains both a subject and predicate, can stand alone as a sentence (a simple sentence), or be a part of a multi-clause sentence. Coordinating conjunctions (and, but, for, nor, or, so, yet) are used to connect elements of equal weight such as two independent clauses, using a comma before the conjunction.
We visited Paris last September.
[independent clause functioning as a full sentence]
We visited Paris in September, and then we visited Berlin in October.
[two independent clauses connected by the coordinating conjunction and preceded with a comma]
3. A dependent clause (or subordinate clause) contains both a subject and a verb but cannot stand alone as a sentence. It must always be a part of a sentence, on which it depends for meaning. Reading a dependent clause on its own leaves the reader wondering where the rest of the information is. The following sections describe the different kinds of dependent clauses.
4. An adverb clause or adverbial clause (also called a subordinate clause) is a type of dependent clause which starts with a subordinating conjunction (e.g. because, although, when, if, until, as if etc.). It indicates a dependent relationship with information elsewhere in the independent clause that it modifies. Similarly to adverbs, adverb clauses usually answer questions such as: Why? How? When? Under what circumstances? When the adverb clause is written before the independent clause, separate the two with a comma.
In the following example pairs, see how the same information is given using a word, phrase or a clause.
We ate dinner at the hotel bistro.
[the adverbial phrase modifies the verb ate; it answers the question where?]
We ate dinner where all the locals usually go to.
[The adverb clause modifies the verb ate; it answers the question where?]
We wanted to go to the Louvre early.
[The adverb modifies the verb phrase wanted to go; it explains when?]
We wanted to go to the Louvre as early as we could.
[The adverb clause modifies the verb phrase wanted to go; it explains when?]
We visited Paris last September due to a business meeting.
[The adverbial phrase explains why?]
We visited Paris last September because we wanted to see the Mona Lisa at the Louvre museum.
[The adverb clause modifies the entire independent clause; it explains why?]
5. An adjective clause (also called a relative clause), just like an adjective, modifies the noun or pronoun preceding it (also called the antecedent). It starts with a relative pronoun (e.g. who, which, that, where, when, whose, whom, whoever etc.) which is also the subject of the clause.
In the following example pairs ,see how the same information is given using a word, phrase or a clause.
This is a great museum.
[the adjective amazing modifies the noun museum]
This is a museum that we visited last year.
[The adjective clause modifies the noun museum; that is a relative pronoun referring to the antecedent museum]
In Paris, we met good friends.
[the adjective good modifies the noun friends]
In Paris, we met friends whom we haven’t seen for years.
[the adjective clause modifies the noun friends; whom is a relative pronoun referring to the antecedent friends]
6. Use who, whom, whoever and whomever when the adjective clause refers to a person or an animal with a name. Use which or that when the adjective clause refers to a non-person (thing) or an animal that is not a pet.
The French lady who was our tour guide turned out to be a distant relative of ours.
[the French lady is a person; who is used]
Our hotel, which was built in 1830, had an excellent bistro.
[our hotel is a thing; which is used]
7. When an adjective clause is non-restrictive (gives an extra piece of information not essential to the overall meaning of the sentence), separate it with commas from the rest of the sentence. Do not use that with non-restrictive adjective clauses.
The hotel that was built in 1830 has an excellent bistro
[The adjective clause is restrictive; only the hotel built in 1830 has an excellent bistro. The adjective clause is essential to the meaning of the sentence]
The hotel , which was built in 1830, had an excellent bistro.
[The adjective clause is non-restrictive; there may be more hotels with excellent bistros. The adjective clause merely adds extra information]
8. A noun clause functions as a noun, meaning that it can be a subject, object or complement in a sentence. It starts with the same words that begin adjective clauses: that, who, which, when, where, whether, why, how.
The Louvre museum was amazing!
[The Louvre museum = noun phrase as subject of sentence]
What we saw at the Louvre Museum was amazing.
[What we saw at the Louvre Museum = noun clause as subject of sentence]
We loved what we saw at the Louvre museum.
[what we saw at the Louvre museum = noun clause as object of the verb like]
The best thing we liked was what we saw at the Louvre museum.
[what we saw at the Louvre museum = noun phrase as complement of the verb was]
9. Do not confuse between adjective and noun clauses, as they begin with the same words. A word starting an adjective clause has an antecedent to which it refers, whereas a word starting a noun clause does not.
Our French friends know that we saw the new exhibition at the Louvre.
[that we saw the new exhibition at the Louvre = noun clause as object of the verb know]
The new exhibition that we saw at the Louvre was amazing.
[that we saw at the Louvre = adjective clause referring to the antecedent exhibition]
10. An elliptical clause may seem incorrect as it may be missing essential sentence elements, but it is actually accepted grammatically. As these clauses must appear together with complete clauses which contain the missing words, repetition is avoided by leaving the same words (or relative pronoun) out in the elliptical clause. This conciseness actually adds to the flow of the text and promotes writing that is more elegant.
In the following examples, the omitted words are given in parenthesis.
The Louvre museum was one of the sites (that) we did not want to miss.
[The relative pronoun that is omitted from the adjective clause]
After (we visited) the Louvre, we went out to dinner at a French bistro.
[subject and verb omitted from adverb clause]
The French make better croissants than the American (make or do).
[second half of comparison omitted]