No, 'turn' can be a verb or a noun.
irregular adjective is a comparing three or more thing/persons.. 1.positive 2.comparative 3.superlative
The only adjectives in the English language which are irregular are some in the type known as 'comparatives and superlatives'. 1. Examples of regular comparative/superlative adjectives: Big, bigger,...
Roman
I think you mean nostalgia, the adjective form of nostalgia is nostalgic.