Which of the following demonstrates affixation?

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

Answer: (A)

Affixation is adding a bound morpheme to a base word to form a new word or a different word class. Here, the suffix -ful is attached to the base use to create useful, an adjective meaning able to be used. This shows affixation in action: a suffix is added to a root to change its meaning and grammatical category. The other options don’t illustrate this process—the base word use has no affix, the form usefuly isn’t a standard word (the correct adverb would be usefully, with -ly), and tidy is also a base form without affixation.