Which of the following demonstrates affixation?

• A. Useful
• B. Use
• C. Usefuly
• D. Tidy

Answer: (A)

Affixation is forming a new word by adding an affix to a base word. Here, attaching the suffix -ful to the base use creates useful, turning a verb into an adjective that means “able to be used” or “providing utility.” This demonstrates affixation clearly because a suffix changes both form and meaning.

The base word use isn’t affixed, so it doesn’t illustrate the process. The form that isn’t a standard word isn’t a valid example of affixation in ordinary use, and tidy is a completely different word not derived from use with an affix.