誕生日
たんじょうび · tanjoubi · JLPT N5 · noun
birthday
🎂 誕生日 = be born (誕) + birth/life (生) + day (日)
誕生 (tanjou) means birth, and 日 (bi, voiced from hi) means day, so the word is literally birth-day, built just like the English. The same 日 ends weekday names such as 日曜日 (nichiyoubi).
生 — sprout 屮 above earth 土
Originally a pictograph showing a young plant sprouting from the ground, with 屮 (a sprout) above 土 (earth). The core meaning is 'to be born, to grow, to live,' which extends to 'raw, unripe, unfamiliar.' The modern form has simplified the sprout shape but preserves the image of new growth emerging from soil.
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'.