yes·ter·day 
(yĕstər-dā′, -dē)
(yĕstər-dā′, -dē)n.
1. The day before the present day.
2. also yesterdays Time in the past, especially the recent past.
adv.
1. On the day before the present day.
2. A short while ago.
[Middle English, from Old English geostran dæg : geostran, yesterday; see YESTER- + dæg, day; see DAY.]