[Sun.day] n [ME, fr. OE sunnandaeg (akin to OHG sunnuntag), fr. sunne sun + daeg day] (bef. 12c): the first day of the week: the Christian analogue of the Jewish Sabbath -- Sun.days adv
[2]Sunday adj (14c) 1: of, relating to, or associated with Sunday
2. [fr. the practice of wearing one's best clothes on Sunday to attend church]: best "~ suit"
3: amateur "~ painters"