Down is a versatile word in English with multiple meanings:
1. As an adverb: indicating direction (downstairs), position (sit down), or state (write down)
2. As a preposition: indicating movement from higher to lower position (walk down the street)
3. As an adjective: meaning depressed or not functioning (feeling down, the system is down)
4. As a noun: referring to soft feathers or a state of misfortune (ups and downs)
5. In sports: one of four attempts to advance the ball in American football
6. Slang usage: meaning "cool with it" or "understand" (I'm down with that)