Emily Dickinson Lexicon

SEV'EN-NIGHT, n. [seven and night.]

A week; the period of seven days and nights; or the time from one day of the week to the next day of the same denomination preceding or following. Our ancestors numbered the diurnal revolutions of the earth by nights, as they reckoned the annual revolutions by winters. Sevennight is now contracted into Sennight, – which see.