air
The word 'aria' in Italian is used to refer to air, atmosphere, or climate. It can also refer to a melody or tune, especially in opera. In this context, 'aria' is used to refer to the substance that we breathe.
The air is very fresh today.
In this sentence, 'aria' is used in its most common sense to refer to the mixture of gases that forms the Earth's atmosphere that we breathe. The adjective 'fresca' describes the air as being cool and refreshing.
There is no air in this room.
This phrase uses 'aria' to describe the feeling of the atmosphere inside a room. Saying 'non c'è aria' usually means the room is stuffy or it's hard to breathe, not that there's an actual absence of air.
Spring air.
This phrase refers to the characteristic feel of the atmosphere during the spring season. This can include various things like the temperature, smells, humidity, etc., that people associate with spring.