Collective noun
A collective noun denotes a collection of individual persons or objects. Examples are: jury, army, committee, team, herd etc.
In British English a collective noun may be treated either as singular or as plural. In American English a collective noun is always treated as singular.

Colon
The colon (:) is a punctuation mark that is almost always used after a complete sentence. A colon indicates that what follows is an explanation of what precedes. Note that a colon is not preceded by a white space, and it is not followed by a hyphen.

Common gender
A label which can denote people of either sex. Examples are: teacher, child, doctor and student.

Common noun
A noun which denotes a class of things. Examples are: dog, boy, student, man, kite etc.

Comparative
The term comparative refers to that form of an adjective or adverb which is constructed with either –er or more. The comparative form of an adjective or adverb expresses a higher degree of the quality denoted by the positive (base) form.
Examples are: taller, stronger, sharper, more beautiful, more careful etc.
Note that English also has a comparative of inferiority. This form is constructed with less. Example: less interesting

Comparative clause

A clause attached to a comparative adjective or adverb.
Examples are given below:

Alice is taller than I am. (Here the group of words ‘than I am’ is a comparative clause attached to the comparative taller.)

Complex sentence
A sentence which contains at least one subordinate clause. In the following examples subordinate clauses are given in bold text.
Alice said that she was not coming.

Compound
The grammar term compound denotes a word constructed by combining two or more words. Note that in many cases the meaning of a compound is not predictable from the meanings of its component parts.

Compound sentence
A sentence which contains two or more main clauses but no subordinate clauses is called a compound sentence. Note that the clauses in a compound sentence are usually connected by conjunctions such as and, or or yet.