poetic license

noun

1. license or liberty taken by a poet, prose writer, or other artist in deviating from rule, conventional form, logic, or fact, in order to produce a desired effect.

Word History and Origins

Origin of poetic license¹

First recorded in 1780–90

Idioms and Phrases

Also, artistic license. The liberty taken by a writer or artist in deviating from conventional form or fact to achieve an effect. For example, I've never seen grass or a tree of that color; but that's artistic license. [Late 1700s]