-er or -or? Is There a Rule for an Agent Noun Suffix?

Agent noun suffixes change verbs into active nouns and are assigned according to the origin of the word being adapted. Latin words get -or, and almost everything else gets -er.

This rule, and in fact the part of speech, can be incredibly confusing. So, here is a breakdown of what agent nouns are, how they’re used, and how to form them with the correct suffix.

What is an Agent Noun Suffix?

An agent, in general terms, is the perpetrator of an action. When used to talk about nouns, this simply means that the noun is performing some kind of action in the sentence; they are the “doer” of the idea being presented. Agent nouns are created by transforming a verb using a specific suffix. These suffixes are -er and -or.

  • Regular verb: Act
    • Agent noun: Actor
  • Regular verb: Run
    • Agent noun: Runner

Agent nouns are not to be confused with recipient nouns, which are the “takers” of the idea. Recipient nouns have actions done or given to them, and are passive where agent nouns are active. They’re formed in much the same way, but with the suffix -ee.

  • Regular verb: Employ
    • Agent noun: Employer
    • Recipient noun: Employee

Should you use -er or -or?

There are two common suffixes for agent nouns: -er and -or.

-er is the more commonly used suffix for agent nouns in English. There isn’t a specific rule associated with it. -or, on the other hand, is less commonly used than -er, but still common enough to be confusing for writers.

The basic rule associated with -or is that words of Latin origins use it to become agent nouns. These are words like auditor (from the Latin audire, “to hear”) and spectator (from the Latin spectare, “to observe”).

It’s difficult to tell at a glance if a word is Latin-based, so the best method for learning which nouns this suffix is applied to is simply observation and memorization. Take notes of which words you see ending in -or, and try to apply the suffix to similar words in the future.

It may take some trial and error, but once you get it, you can expand your repertoire of agent nouns. If you’re unsure or need a quick answer, consult a dictionary or look up a list of Latin root words that are commonly used in English to find the etymology of the word you’re using. This can give you a sense of which suffix to use.


This distinction is one of the fiddlier sets of rules in English; suffixes, or the additions we make to the ends of words to enhance or change their meanings, are a complicated subset based on seemingly arbitrary rules. They don’t have to be this challenging, though.

As long as you remember what your word is doing (or having done to it) and can find out where it came from, you should be able to make agent nouns with no problems.