These punctuation marks are not typical for definite languages, and their visible similarity may be confusing for a person unfamiliar with their meaning and purpose.
1) Colon [ :] should be used (a) before a list or (b) an explanation that is preceded by a clause that can stand by itself. Think of the colon as a gate, inviting one to go on:
- Example: This decision called for only one course of actions: revolt! (b)
- Example: This sentence contains the following parts of speech: a noun, an adjective and a verb. (a)
2) Semicolon [;] is used: to (a) connect two independent clauses together into one sentence, (b) as a super-comma, (c) between items in a series or listing containing internal punctuation:
- Example: This could be a complete sentence; this could be another one.
If you put a comma where that semicolon is, you will have committed a “comma splice,” which is a nasty grammar error.
There is, however, one exception that can cause you a problem. You don’t use a semicolon to connect two complete sentences if there’s a conjunction between the clauses (and, but, etc.). In that case, use a comma:
- Example: This could be a complete sentence, and this could be another one.
Adding that single word, the conjunction “and,” means that you must change that semicolon into a comma.
