Word Number 3
yesterday
Primary Chinese
昨天
Primary Pinyin
zuó tiān
Short Definition
The day immediately before today.
Primary Meaning
今天之前的一天
Primary Note
Previous-day time expression.
Mapping Boundary
Correct: Yesterday I buy phone → 昨天我买手机。
Incorrect: Yesterday I bought phone as the canonical token sequence
The time word carries past reference; buy remains canonical.