PUNCTUA'TION, noun In grammar, the act or art of pointing a writing or discourse, or the act or art of marking with points the divisions of a discourse into sentences and clauses or members of a sentence. punctuation is performed by four points, the period (.); the colon (: ); the semicolon ( ; ); and the comma (, ). The ancients were unacquainted with punctuation; they wrote without any distinction of members, period or words.