In oracle bone script, 八 was a picture of two lines splitting apart — the original meaning was "to divide / separate". The character was reborrowed for the number eight, and the original "divide" meaning moved to 分 (= 八 + 刀, splitting with a knife). Identical across 繁體 / 新字体 / 简体.

Cultural note — the lucky number par excellence. In Mandarin, 八 (bā) sounds nearly identical to 發 / 发 (fā, "to prosper / get rich"). The pun makes 8 the most auspicious number in Chinese-speaking culture, far more powerful than 6. Real estate addresses with 8s sell at premiums; license plates with multiple 8s auction for tens of thousands of dollars; 8:08 on August 8, 2008 was the chosen start time for the Beijing Olympics opening ceremony. Phone numbers ending 8888 are luxury items. If you understand only one cultural-numerology fact about Chinese, make it this one.

In Cantonese, the pun is even stronger: 八 (baat³) and 發 (faat³) rhyme cleanly.

Mandarin: bā, level 1st tone. 八月 (bāyuè, August), 八十 (bāshí, eighty), 八卦 (bāguà, the Eight Trigrams of the I Ching — and modern slang for "gossip"), 八点 (bā diǎn, eight o'clock).

Japanese: on-reading ハチ (hachi) for everyday counting — 八月 (hachigatsu, August), 八時 (hachiji, eight o'clock), 八十 (hachijū, eighty). Kun-reading や (ya) appears in 八つ (yattsu, eight items) and the irregular date 八日 (yōka, eighth day of month).

The number is also auspicious in Japan — 八 visually opens outward, suggesting widening prosperity. The phrase 末広がり (suehirogari, "widening at the end") describes both the visual shape and the metaphorical fortune.

Financial form: 捌 prevents alteration on contracts.

Memory aid: two strokes leaning apart — the original "splitting" picture preserved exactly.