昨日
きのう · kinou · JLPT N5 · noun
yesterday
📅 昨日 = past (昨) + day (日): the day just gone
昨 means previous or last, and 日 means day, so the compound is literally the previous day. The reading きのう is a special one for the whole word, not built from the kanji sounds. Sound hook: kinou, the day you already KNOW.
日 — pictograph of the sun
日 is a pictograph of the sun, originally drawn as a circle with a dot or stroke inside representing the sun's substance. Over time the round shape was squared off into the modern rectangular form. It means 'sun' and by extension 'day'.