September definition by Webster's New World
Origin: Middle English and amp; Old French Septembre ; from Classical Latin September ; from septem, seven (+ -ber ; from uncertain or unknown; perhaps ): so named as the seventh month of the ancient Roman year, which began with March
September definition by American Heritage Dictionary
noun Abbr. Sept.
Origin: Middle English Septembre, from Old French, from Latin September, the seventh month, from septem, seven; see septm̥ in Indo-European roots.