English uses two spellings to label a person who performs an action: -er and -or. They sound identical (/ər/) but follow different rules. Once you know the pattern, you stop guessing.
The Quick Rule
- -ER attaches to verbs of native English origin and most modern verbs (teach → teacher, work → worker, drive → driver, write → writer).
- -OR attaches to verbs of Latin origin, especially those ending in -ATE, -CT, -SS, -IT (act → actor, edit → editor, profess → professor, direct → director).
Practice Words
The Latin Endings That Take -OR
If the verb ends in any of these patterns, expect -OR:
- -ATE verbs: educate → educator, narrate → narrator, calculate → calculator.
- -CT verbs: act → actor, conduct → conductor, direct → director.
- -SS verbs: profess → professor, confess → confessor, possess → possessor.
- -IT verbs: edit → editor, audit → auditor, inspect → inspector (note -CT here).
- Most other Latinate verbs: invent → inventor, oppress → oppressor, sponsor.
The Common -ER Verbs
Most everyday English verbs take -ER:
- Native verbs: teacher, baker, runner, helper, fighter, singer, swimmer.
- Modern coinages: blogger, gamer, programmer, designer.
- One-syllable verbs: maker, taker, giver, buyer, lover.
Pronunciation Is Identical
Both endings sound exactly the same: /ər/ in American English, /ə/ in British English. So the rule is purely a spelling rule — your speech is never affected. But getting the spelling right marks you as a careful writer.
Memory Trick
Latin → -OR. Native or modern → -ER. When in doubt, ask: "Does this verb end in -ATE, -CT, -SS, or -IT?" If yes, use -OR. Otherwise, default to -ER.
The Few Tricky Ones
- sailor, tailor — not from -ATE verbs but still take -OR (older Latin trade words).
- liar, beggar — neither -ER nor -OR; older spellings.
- adviser/advisor — both spellings are accepted; -OR is more formal/American.
The rule covers about 95% of cases. The rest you learn by reading.