The difference between sunny day and sunny day

Sunny day: sunny day; Sunny; Sunny; Good lighting; Full of light; Sunward; (color, etc. ) Like the sun, golden yellow;

Sunny day: it is a noun, which means sunny day; Sunny weather

Adjective (English: adj.) is a kind of part of speech, which is mainly used to describe or modify nouns or pronouns, indicating the nature, state, characteristics or attributes of people or things, and is often used as attribute, predicate or complement.

Noun (English: noun, abbreviated as N.) is a part of speech and belongs to content words. It represents a unified name for people, things, things, places or abstract concepts. Divided into proper nouns and common nouns.