Formal English - "Food for thought"

Question

Is the phrase "food for thought" considered to be formal or informal?

Answer 1

The phrase "food for thought" is considered an idiom. Idioms are used for informal speaking and writing. If you are doing creative writing, it is acceptable to use an idiom or colloquialism. In a formal writing, such as a research paper, it is best to avoid idioms. They can be seen as unprofessional and informal.