Inflection Vs. Derivation
Inflection is the process of adding inflectional morphemes (smallest units of meaning) to a word, which indicate grammatical information (for example, case, number, person, gender or voice, mood, tense, or aspect). Derivation is the process of adding derivational morphemes, which create a new word from existing words, sometimes by simply changing grammatical category (for example, changing a noun to a verb).
Words generally are not listed in dictionaries (in which case they would be lexical items) on the basis of their inflectional morphemes. But they often are listed on the basis of their derivational morphemes. For instance, English dictionaries list readable and readability, words with derivational suffixes, along with their root read. However, no traditional English dictionary lists book as one entry and books as a separate entry nor do they list jump and jumped as two different entries.
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