Mud is the root word. If I add -dy to make the word muddy, is that suffix a derivational or inflectional morpheme?

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    That's a 'derivational morpheme' because it does change the part of speech of the word. 'Mud' is a noun and 'muddy' is an adjective. (BTW, the suffix is -y, not -ddy.) Dec 28, 2020 at 16:22
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    Right. It's derivational. Here's a handout on the subject. Dec 28, 2020 at 16:32

1 Answer 1


The suffix in the word muddy is -y, which is an adjective-forming suffix usually added to nouns and verbs. The root word in muddy is mud.

'Inflectional morphemes' are ones that don't change the part of speech of a word, for instance, the plural suffix -s or the past tense marker -ed:

  • bag → bags (both are nouns)
  • want → wants, wanted (all of them are verbs)

'Derivational morphemes' on the other hand are ones that do change the part of speech of a word. For example, suffixes like -y, -ise/-ize etc:

  • mud (noun) → muddy (adj)
  • standard (noun or adj) → standardise (verb)
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    See also slime, slimy; haste, hasty; fish, fishy; health, healthy, ... Apr 4 at 1:35

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