多 (duō) is a basic adjective meaning 'many, much, a lot' — it goes directly before nouns (多人 'many people'). For 'many', the colloquial 好多 (hǎo duō) and the more formal 许多 (xǔ duō) are common alternatives, but 多 is the simplest and most versatile. 多 also serves as an interrogative 'how' before adjectives (多大 'how big?') and as a suffix after numbers to mean '...-odd, more than' (十多个 'ten-odd').