Subject-verb agreement means that the verb must agree with its subject in person and number. To review person and number, let’s look at some verb conjugations.
Possibly because of speaking habits, many people fail to put the “s” on the 3rd person singular. We need to hear and write:
- He knows the answer.
- She sees the solution.
But remember there is no “s” on the first person verb.
- I understand the problem.
- Not – I understands the problem.
Since you don’t always write with pronouns as the subject of your sentence, you need to see how this works with a noun:
- The train runs down the track.
- Trains run down the track everyday.
Notice here that when the subject does not have an “s,” the verb does, and vice versa.
If you are making this kind of subject-verb agreement error, you need to learn what endings are needed and to listen carefully for whether you have put on or left of an ending.