需要 (xūyào) is the standard, neutral word for 'to need' — it works for both concrete needs (a glass of water) and abstract requirements (effort, time). It's more general than 要 (yào 'to want'), which often implies personal desire or intention, and less formal than 要求 (yāoqiú 'to demand, to request'), which is used when making a specific request or setting a requirement. As a noun, it means 'needs' (e.g., 他的需要 'his needs').