In the word 'disinterested', which part is a free morpheme?

• A. Dis-
• B. -ed
• C. Interest
• D. Dis- and -ed

Answer: (C)

A word can be built from units that either can stand alone or must attach to something else. In disinterested, interest is a complete word by itself and carries its own meaning, so it can function as a free morpheme. The pieces dis- and -ed can’t stand alone—they’re bound morphemes: dis- is a prefix that attaches to a base, and -ed is a suffix that attaches to a base to form a participle or adjective. So the word is formed from dis- plus interested, with interest serving as the core base that remains a standalone word.