You can attach modifiers (adjectives and other nouns) to nouns in most of the places you can use nouns.  For example:

Angry cats are dangerous

Tells the system that cats are dangerous when they are also angry.  But doesn’t say that non-angry cats need be dangerous or non-dangerous.  Right now there’s no construction like cats are dangerous only when they’re angry.  But you could achieve the same end in this case, but adding:

Angry cats are dangerous
Dangerous cats are angry

These two statements together would specify that cats are dangerous if and only if they’re angry.

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