Derivational morphemes create new words or change a word’s part of speech, while inflectional morphemes modify a word’s form to fit grammatical context without changing its core meaning. The distinction matters because these two types of word-building pieces behave very differently in English, following separate rules about where they attach, how many exist, and what they do to the words they join.
What Derivational Morphemes Do
A derivational morpheme attaches to an existing word to produce a new word with a different meaning, a different part of speech, or both. Take the word “friend.” By adding derivational morphemes, you can build an entirely different set of words: “friendship” and “friendliness” (nouns), “friendly” and “friendless” (adjectives), and “befriend” (a verb). Each result is a distinct word with its own dictionary entry and its own meaning.
The most important thing derivational morphemes do is change a word’s grammatical category. Suffixes like -ment and -ness turn verbs and adjectives into nouns (“argue” becomes “argument,” “happy” becomes “happiness”). Suffixes like -ify and -ize turn nouns into verbs (“beauty” becomes “beautify,” “modern” becomes “modernize”). Suffixes like -ful and -ish turn nouns into adjectives (“hope” becomes “hopeful,” “girl” becomes “girlish”). There are several hundred derivational suffixes in English, and derivational morphemes can also be prefixes: “un-” in “unhappy,” “re-” in “rebuild,” “be-” in “befriend.”
Here are some of the most common noun-making derivational suffixes to illustrate the pattern:
- -acy: state or quality (privacy)
- -dom: place or state of being (freedom, kingdom)
- -er, -or: one who (trainer, protector)
- -ism: doctrine or belief (communism)
- -ment: condition of (argument)
- -tion, -sion: state of being (transition, concession)
What Inflectional Morphemes Do
Inflectional morphemes don’t create new words. They create variant forms of existing words to signal grammatical information: tense, number, possession, comparison. When you add -s to “dog” to get “dogs,” you haven’t made a new word. You’ve made the same word plural. The core meaning is unchanged.
English has exactly eight inflectional morphemes, and all of them are suffixes:
- -s, -es (plural): dog → dogs
- -‘s (possessive): dog → dog’s
- -s (third person singular present): she walks
- -ed (past tense): walked
- -en, -ed (past participle): broken, walked
- -ing (present participle): walking
- -er (comparative): taller
- -est (superlative): tallest
That’s the complete list. Unlike the hundreds of derivational morphemes, inflectional morphemes form a small, closed set. An inflectional morpheme never changes a word’s part of speech. “Walk,” “walks,” “walked,” and “walking” are all forms of the same verb.
Productivity: Who Plays Well With Others
One of the sharpest differences is productivity, meaning how freely a morpheme combines with other words. Inflectional morphemes are highly productive. The plural -s can attach to nearly any noun, in the same form, with the same predictable effect. You can pluralize “cat,” “phone,” “algorithm,” or any new noun that enters the language tomorrow.
Derivational morphemes are picky. The suffix -hood works with “brother,” “neighbor,” and “knight,” but not with “friend,” “daughter,” or “candle.” You can’t predict which base words will accept which derivational suffix. The meaning can also be inconsistent: “brotherhood” means the state of being brothers, but “neighborhood” doesn’t mean the state of being neighbors. This selectivity and unpredictability is a hallmark of derivational morphology.
Attachment Order
When both types appear on the same word, they follow a strict rule: all derivational morphemes attach before any inflectional ones. Consider the word “nationalizations.” The base word is “nation” (a noun). First, derivational suffixes build the word outward: “nation” + -al (adjective) + -ize (verb) + -ation (noun). Only after all that derivational work is done does the inflectional plural -s attach at the very end.
You’ll never find an inflectional morpheme sandwiched between derivational ones. This ordering rule is absolute in English. It reflects a deeper principle: derivational morphemes build the word itself, while inflectional morphemes adjust the finished word to fit its role in a sentence.
Position in the Word
In English, inflectional morphemes are always suffixes. They only attach to the end of words. Derivational morphemes, by contrast, can be either prefixes or suffixes. Prefixes like “un-,” “re-,” “dis-,” and “pre-” are all derivational. So are suffixes like “-ness,” “-able,” and “-tion.” This flexibility is another easy way to tell the two apart: if it’s a prefix, it’s derivational.
A Side-by-Side Comparison
Pulling the key differences together:
- Meaning change: Derivational morphemes create a new word with a new meaning. Inflectional morphemes create a grammatical variant of the same word.
- Part of speech: Derivational morphemes often change it (noun to verb, adjective to noun). Inflectional morphemes never do.
- Number: English has several hundred derivational morphemes but only eight inflectional ones.
- Position: Derivational morphemes can be prefixes or suffixes. Inflectional morphemes are always suffixes.
- Productivity: Inflectional morphemes attach freely and predictably to nearly all words in a category. Derivational morphemes are selective and sometimes unpredictable.
- Order: Derivational morphemes always attach closer to the root. Inflectional morphemes always come last.
Tricky Cases to Watch For
Some suffixes look identical but serve different functions depending on context. The suffix -er is inflectional when it marks a comparative adjective (“taller”), but it’s derivational when it turns a verb into a noun meaning “one who does something” (“teach” → “teacher”). The test is simple: did the suffix change the word’s part of speech or create a new meaning? If yes, it’s derivational. Did it just adjust the same word for grammar? Inflectional.
The suffix -ing can also cause confusion. In “she is walking,” -ing is an inflectional morpheme marking the present participle. But in “the walking was tiring,” where “walking” functions as a noun, a case can be made that -ing has shifted the word’s category. In practice, most introductory linguistics courses treat -ing on verbs as inflectional and focus the derivational label on suffixes that more clearly create new dictionary entries.
If you remember one core principle, it covers most situations: inflectional morphemes are grammar tools that fine-tune a word for its sentence, while derivational morphemes are word-building tools that manufacture new vocabulary from existing pieces.