light
The German word for 'light' is 'Licht'. It is used to describe both the natural phenomenon that makes things visible and the artificial sources of illumination. For example, 'Das Licht der Sonne' means 'The light of the sun' and 'Die Lampe gibt Licht' means 'The lamp gives light'.
The light in my room is very bright.
This is telling that the light in the speaker's room is very bright. In German, noun capitalization is mandatory hence 'Licht' being capitalized.
The light at the end of the tunnel is hope.
This is a common phrase used in both English and German to express that there is a reason for optimism even in difficult times, using 'light at the end of the tunnel' metaphorically.
He turned off the light and went to sleep.
This sentence is describing an action where a person turns off the light before going to bed. 'Licht aus' means 'light off'.