Question

which of the following words uses the hyphen incorrectly?
seven-year-old
mother-in-law
mid-september
vice-president

Explanation:

To determine incorrect hyphen usage, analyze each option:

• "Mother - in - law": Correct (compound noun with hyphens).
• "Mid - September": Correct (hyphen in compound adjective for a month).
• "Vice - President": Correct (hyphen in compound noun).
• "Seven year old": Incorrect. When used as an adjective (e.g., "a seven - year - old child"), "year" should be hyphenated and singular. As a phrase ("He is seven years old"), no hyphens, but as an adjective, it should be "seven - year - old". Here, "seven year old" (without proper hyphenation for the adjective form) is wrong.

Answer:

Seven year old