The semicolon is similar in name and appearance to the colon, but its function is unrelated; it serves as a weak period, as employed here, or as a strong comma, as shown in the next paragraph. In its weak-period guise, it marks the end of one statement and the beginning of another; however, it is appropriate in place of a period only if the second statement is closely related to or dependent on the first one. Note that when a semicolon appears in such a case, no coordinating conjunction (such as and or but) should follow it. (However, when the conjunctive adverb that begins this sentence, or others such as moreover or therefore, follows a semicolon, as occurs earlier in this paragraph, a comma should follow the word.)
A strong-comma semicolon is one used in place of two or more commas when the elements in a run-in list are themselves lists, as in this sentence: “The three most frequent color schemes in flags are red, white, and blue; red and white; and, tied for third place, red, yellow, and green and red, white, and green.” (Note that not all list items must include internal punctuation.)
Many writers are reluctant to use semicolons because they do not understand how to use the punctuation mark correctly or consider it overly formal, but its roles are simple and helpful.
