「水」 (mizu) means "water." It's a clear, colorless, odorless, and tasteless liquid essential for all known forms of life. You use 「水」 when asking for a glass of water or talking about drinking water. 「水をください。」 (Please give me water.) is a common request.

透明で、生きるために必要な液体です。飲む時や洗う時に使います。