Several parts combine into one character.

Three horizontal strokes — the last "obvious" number. The pictographic counting series breaks at 四: from 4 onward, characters use phonetic loans rather than continuing to add lines (otherwise 9 would be a tangle of strokes nobody could read). Identical across 繁體 / 新字体 / 简体.

Three carries cultural weight across East Asia. The number is associated with completeness and stability: 三才 (sāncái, "the Three Talents" — Heaven, Earth, and Humanity, the foundational Confucian cosmology), 三國 / 三国 (Three Kingdoms — the iconic 3rd-century period dramatized in 三国志 / Sangokushi / Romance of the Three Kingdoms), 三十六計 (Thirty-Six Strategies, classical Chinese strategy text). Buddhist 三宝 (Three Treasures: Buddha, Dharma, Sangha). Three is "enough but not excess" — the natural rest point.

Mandarin: sān, level 1st tone. 三月 (sānyuè, March), 三角 (sānjiǎo, triangle), 三明治 (sānmíngzhì, sandwich — phonetic loan: "san-ming-zhi"). The same tone as 山 (mountain), but shorter syllable and very different rhyme.

Japanese: on-reading サン (san) is identical to 山 — context disambiguates. 三月 (sangatsu, March), 三角形 (sankakkei, triangle), 三人 (sannin, three people — note this one is regular, unlike 二人/futari). Kun-reading み (mi) survives in 三日 (mikka, third day of month — irregular but common) and 三つ (mittsu, three items).

Financial form: 参 (also written 參) prevents forgery on financial documents. Adding two strokes to 三 to make 五 was historically too easy.

Memory aid: three lines stacked, with the middle line slightly shorter (calligraphic convention).