noun which may take the genitive case particle 'no'
unfriendly; non-friendly
Used as a no-adjective to describe relations, attitudes, or environments that lack friendliness or goodwill. Often appears in formal or diplomatic contexts.
Relations between the two countries remain unfriendly.
I was surprised by the unfriendly attitude I received.
Formed from the prefix 非- (non-) and 友好 (friendship). The prefix 非- is productive for forming no-adjectives with a meaning of 'non-' or 'un-'. The exact historical derivation is straightforward.