Examples

In these words to live by, the "One –S" rule shows us that the subject and verb agree because the singular subject student doesn't have an –s on the end, and submits sure does.

In this (very true) sentence, we have a plural subject, songs. Since it ends in –s, we know the verb, sound, should not end in –s if we want it to agree with the subject.

Hold up. There's no –s on the subject, children, and there's no –s on the verb, run. What gives? We told you that the "One –S" rule works for most sentences. It doesn't work for all of them. Some rule-busting subjects—like children, women, men, and fungi (hmmm, one of these things is not like the others) don't take an –s when they become plural, so you're going to need to keep an eye out for them.