Fill in the Blanks Commas and SemicolonsOnline version Review of commas and semicolons by Dawn Rookey 1 comma introductory semicolon list period Inside Punctuation Definition : . Use a comma to separate words or items in a . Use a in place of a period for two sentences where the conjunction has been left out . Usa a and a conjunction when separating two complete thoughts . Use a semicolon in place of a for two sentences where the conjunction has been left out . Use a comma when there are words that being a sentence like : namely , however , therefore , or for example .