昌

Top sun radical, four strokes — a rectangle with one horizontal inside, the disc of the sun. Anchors 昌 in the brightness family. With the speaking-mouth below, the character originally meant 'bright speech, fair words,' from which came 'flourishing, prosperous.' Same sun family: 明 (bright), 时 (time), 春 (spring).

Bottom 曰 — wider and squatter than 日, a mouth with a horizontal tongue or breath-line inside, meaning 'to say.' Below the sun, 昌 reads as 'speech in broad daylight' — open, bright, clear. From that came 'flourishing,' as in the surname 昌 and place name 昌平.