大约

大约 (dàyuē) is an adverb meaning 'approximately,' 'about,' or 'roughly.' It comes before a number or quantity to signal an estimate: 大约二十个人 ('about twenty people'), 大约需要三天 ('takes about three days'). It can also mean 'probably' before a whole clause, though this use is a bit less common than with 大概. English speakers should note that 大约 tends to attach to measurable quantities — time, amount, distance, number — where English says 'about' or 'around.'

It is neutral in register and slightly more formal or written than the very colloquial 大概 (dàgài), so you'll see 大约 in news and reports as well as speech. Unlike English 'about,' 大约 is an adverb only and cannot itself be a noun or adjective. Pair it naturally with 左右 (zuǒyòu, 'or so') for a doubly hedged estimate: 大约五点左右 ('around five o'clock or so').