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

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

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

Answer: (C)

In word formation, a free morpheme can stand alone as a word. In disinterested, the part that can stand alone is interest, since it’s a complete word with its own meaning. The other pieces, dis- and -ed, are bound morphemes: dis- is a prefix that cannot stand alone and modifies the word’s meaning, while -ed is a suffix that marks tense or participation and also can’t stand alone here. The word is formed by combining interest with -ed to make interested, then adding the prefix dis- to that form, yielding disinterested. So the free morpheme is interest.