Select the most appropriate ANTONYM of the given word.

Colloquial

Formal

The most appropriate antonym of the word colloquial is formal.

• Colloquial means informal or conversational in style.
• Formal means following established rules or conventions.

The other words listed are not antonyms of colloquial.

• Informal means not following established rules or conventions.
• Slack means not strict or demanding.
• Slang is informal language that is not considered to be standard.