yesterday-n; 2 Senses

Sense Number 1: the day before today

Commentary: The day immediately before today. Twenty-four hours ago.

I walked to the bank yesterday, but it was closed.
It seems like just yesterday that I fell down the stairs.
It was in yesterday's newspapers.

WordNet 2.0 Sense Numbers: 1

Sense Number 2: the past

Commentary: The past as a general concept. Usually the recent past.

Yesterday's solutions aren't going to work on the problems of today.
The world of yesterday is a dark, scary place filled with barbarians.
Historians are more concerned with yesterday than tomorrow.

WordNet 2.0 Sense Numbers: 2