What a suffix tells you
A suffix appears at the end of a base or root. It often signals word class and sometimes adds meaning. Compare educate, education, educational, and educationally. The family shares an idea, but each form performs a different grammatical job.
Common noun suffixes
- -tion / -sion: creation, conclusion.
- -ment: improvement, assessment.
- -ness: awareness, effectiveness.
- -ity: ability, reliability.
- -er / -or: researcher, supervisor.
Adjective, verb, and adverb suffixes
- Adjectives: -able/-ible, -al, -ful, -ive, -less, -ous.
- Verbs: -ate, -en, -ify, -ise/-ize.
- Adverbs: -ly, although words such as friendly are adjectives.
Suffixes are useful clues, not mechanical rules. Hard and hardly do not simply differ in word class; their meanings differ substantially.
Spelling changes
Adding a suffix can remove final e (create → creation), change y to i (rely → reliable), or double a final consonant (admit → admission). Pronunciation and stress may also shift: compare photograph, photography, and photographic.
Gap-fill method
- Decide which word class the sentence requires.
- Choose a suffix that can create that class.
- Check spelling and meaning.
- Read the whole sentence aloud to test the collocation.
Example: “The intervention produced a measurable ___ in symptoms.” The article a and adjective measurable point to a noun, so improvement fits.