As nouns the difference between flower and sun

is that flower is a colorful, conspicuous structure associated with angiosperms, frequently scented and attracting various insects, and which may or may not be used for sexual reproduction or flower can be something that flows, such as a river while sun is (astronomy) a star, especially when seen as the centre of any single solar system.

As verbs the difference between flower and sun

is that flower is to put forth blooms while sun is to expose to the warmth and radiation of the sun.

As a proper noun sun is

the star that the earth revolves around and from which it receives light and warmththe illustrated oxford dictionary , oxford university press, 1998.