これを昨日買った。

this (indicating an item near the speaker, the action of the speaker, or the current topic); this person (usu. indicating someone in one's in-group); now; here; I (me); certainly

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

yesterday

to buy; to purchase; to value; to have a high opinion; to stir; to provoke