Here’s a change: the kanji for one, two, and three were simply horizontal lines representing fingers, but this kanji looks decidedly different. What gives?

Historically, the number four was indeed written as 亖, while the ancestor of 四 probably meant breath, but the latter came to be a phonetic substitue for the former, ultimately replacing it entirely. 息 is used for breath.

Vocabulary

Vocabulary Reading Meaning
⭐ 四 し／よん four
⭐ 四つ よっつ four things
四日 よっか fourth day of the month; four days
十四日 じゅうよっか fourteenth day of the month; fourteen days
四月 しがつ April
四角 しかく square
四季 じき four seasons
四十七士 しじゅうしちし the 47 ronin
四月目 よつきめ the fourth month
四つ角 よつかど four corners, crossroads
四回 よんかい four times
四階 よんかい fourth floor