Which term refers to a common expression that has a meaning not deducible from the individual words?

The term that is defined as a common expression with a meaning that cannot be determined from the individual words is "idiom." Idioms are phrases where the overall meaning differs from the literal interpretation of the words within it. For example, the expression "kick the bucket" means to die, which is not evident from the meanings of the words "kick" and "bucket" on their own.

Understanding idioms is essential in language arts because they enrich language, bringing depth and color to communication. They can sometimes present challenges for language learners or readers who take expressions literally instead of recognizing their figurative meaning. This characteristic distinctly sets idioms apart from other terms like literal phrases, proverbs, or figures of speech, which either convey more straightforward meanings or are not inherently tied to idiomatic expressions.