你好

你好 (nǐ hǎo) is the standard Chinese greeting — a literal 'you good' that functions like English 'hello.' Use it on first meeting, when answering the phone in a neutral context (though 喂 wèi is more common), or when greeting someone you do not know well. Two things surprise English speakers: first, 你好 is rarely said between close friends or family, who tend to skip greetings entirely or use 嘿 / 嗨 / 早 instead; second, the second tone on 你 changes to a third tone in 'half-third' pronunciation when followed by another third tone, but tone marks are still written as nǐ hǎo. The polite upgrade for elders and formal contexts is 您好 (nín hǎo).

Note: Works in almost any first-meeting context. For close friends, casual 嗨 or just 嘿 is more common; for elders or strangers in a formal setting, 您好 (nín hǎo) is the polite upgrade.

Memory hook: 'You good?' — literally what you'd say to check someone is well; in Chinese it became the standard hello.