By Marina Pantcheva
A clause is a group of words that includes two obligatory elements:
- a subject – expresses who or what does something. To find the subject, ask who or what performs the activity.
- a predicate – the word expressing the activity. The predicate changes its form depending on the subject (I play but he plays) and depending on the tense (he plays often but he played yesterday). The predicate is always a verb; hence, the easiest way to find the predicate of the clause is to find the verb whose form changes depending on the subject and the tense.
(1) Mary is writing a letter. [Mary is the subject, writes is the predicate]
(2) The new theory captures the data successfully. [the new theory is the subject, captures is the predicate]
There are two types of clauses:
- independent clause – it expresses a complete thought and can stand alone.
(3) John was hired by an IT company.
(4) The majority of politicians do not accept global warming as a real threat.
- dependent clause – it does not express a complete thought but just a part of it. Dependent clauses cannot stand alone.
(5) shortly after he graduated in Computer Science [an incomplete thought]
(6) although scientists have found strong indications of a global temperature rise [an incomplete thought]
Dependent clauses are commonly introduced by special markers (called subordinate conjunctions), such as, if, whether, because, although, since, when, while, unless, even though, whenever (follow this link for a fuller list).
A sentence consists of one or more clauses. A sentence that is made up of a single clause is a simple sentence. The single clause has to be an independent clause in order for the sentence to be complete. The examples in (1)-(4) are all simple sentences consisting of just one independent clause.
A sentence can also contain more than one clause. Such a sentence is called a compound sentence. Compound sentences can consist of two or more independent clauses (connected by and, but, or, nor)
(7) John was hired by an IT company, but Mary did not find a job.
(8) We have to finish the project first, and then we can take a holiday.
A compound sentence can also combine independent clauses with dependent clauses.
(9) Shortly after John graduated in Computer Science, he was hired by an IT company.
(10) The majority of politicians do not accept global warming as a real threat, although scientists have found strong indications of a global temperature rise.
A compound sentence has to contain at least one independent clause to be complete.
Sometimes, complex phrases can be used instead of a dependent clause to encode the same information. This creates a longer simple sentence with just one subject and one verb.
(11) Shortly after his graduation in Computer Science, John was hired by an IT company.
(12) The majority of politicians do not accept global warming as a real threat despite the strong indications of a global temperature rise.
The groups of words “shortly after his graduation in Computer Science” and “despite the strong indications of a global temperature rise” are not clauses because they have no subject (the words John and scientists are missing) and no predicate (graduation is not a verb but a noun derived from a verb).