万

万 (wàn) is the Chinese number 'ten thousand' — and unlike English, it's a core counting unit, not a workaround. Chinese groups large numbers in 万 (10,000) and 亿 (100,000,000), not thousand/million/billion. This is the single biggest mental shift for English speakers: 100,000 is 十万 ('ten ten-thousands'), 1,000,000 is 一百万 ('one hundred ten-thousands'), and 10,000,000 is 一千万 ('one thousand ten-thousands').

Always pause and regroup digits in fours, not threes. 万 also functions figuratively to mean 'a huge number / all / absolutely' in fixed expressions: 千万别 ('absolutely don't,' literally 'thousand-ten-thousand don't'), 万一 ('just in case,' literally 'one in ten thousand'), 万岁 ('long live,' literally 'ten thousand years'). The character is also a common Chinese surname (Wàn).