n.1 a period of seven days reckoned usu. from and to midnight on Saturday-Sunday.
2 a period of seven days reckoned from any point (would like to stay for a week).
3 the six days between Sundays.
4 a the five days Monday to Friday. b a normal amount of work done in this period (a 35-hour week).
5 (in pl.) a long time; several weeks (have not seen you for weeks; did it weeks ago).
6 (prec. by a specified day) a week after (that day) (Tuesday week; tomorrow week).
Etymology: OE wice f. Gmc, prob. orig. sequence