A pure substance is not mixed with anything else.

Something that is pure is clean and does not contain any harmful substances.

If you describe something such as a colour, a sound, or a type of light as pure, you mean that it is very clear and represents a perfect example of its type.

If you describe a form of art or a philosophy as pure, you mean that it is produced or practised according to a standard or form that is expected of it.

Pure science or pure research is concerned only with theory and not with how this theory can be used in practical ways.

Pure means complete and total.

A person, especially a woman, who is described as pure is considered to be morally good, especially because they have no sexual experience or sexual thoughts.

You use pure and simple to emphasize that the thing you are mentioning is the only thing that is involved or that should be considered.