Derivational morphemes is defined as a bound morpheme that is added to a free morpheme to create a new word. For example, adding " -ness" into a word good turns good, which is an adjective, into goodness, a noun.

Derivational morphemes are affixes that are added to a base word to create a new word that may have a different meaning, part of speech, or grammatical function. In psychology, derivational morphemes can be used as part of language assessments or in studies of language acquisition and development.

Examples of derivational morphemes include:

  • "-er" (teacher, baker, runner)
  • "-ist" (artist, therapist, biologist)
  • "-ment" (movement, development, improvement)
  • "-ness" (happiness, kindness, sadness)
  • "-ful" (beautiful, helpful, joyful)
  • "-ize" (analyze, organize, prioritize)
  • "-ly" (quickly, slowly, happily)

Derivational morphemes can also be used to change the tense of a word, such as adding "-ed" to create past tense (walked, talked, played) or adding "-ing" to create present participle (walking, talking, playing).

In psycholinguistics, derivational morphemes are often studied in relation to how they contribute to the meaning and structure of words, and how they are acquired and processed by the brain.