Bound Morpheme

A bound morpheme is a part of a word that cannot stand alone as a word.

Most commonly these are affixes appended on free morphemes, e.g.:

  • -s for plurality
  • -ing for present continuous
  • -ed for past tense

However they can also take the form of cranberry morphemes (morphemes that only occur in one word).

The common example there is, naturally, cranberry (cran/berry). Lukewarm (luke/warm) is another one.

Wikipedia