water
The German word for water is 'Wasser'. It is a noun and is used in the same way as the English word 'water'. For example, 'Ich trinke Wasser' means 'I drink water'.
I need a glass of water.
This sentence is used when asking for a glass of water. In German, 'Ich brauche' means 'I need', 'ein Glas' means 'a glass', and 'Wasser' stands for 'water'.
The water is cold.
This sentence is used to describe the temperature of the water. In German, 'Das' refers to 'The', 'Wasser' means 'water', and 'ist kalt' translates to 'is cold'.
The water comes from the tap.
This sentence is used to express where the water is coming from, the tap for instance. In German, 'Das Wasser' means 'The water', 'kommt aus' translates to 'comes from', and 'der Leitung' stands for 'the tap'.