Look at ownership (possession) with Yossarian the Grammarian regarding apostrophes. Singular and plural nouns are covered.

Enhance your simple past tense verb instruction with this video that clearly demonstrates when to use I was and you were through song and engaging graphics.

A good beat, appealing graphics, and informative lyrics make up a video demonstrating when to use the words like or likes. 

This video provides many examples of how verbs change depending on whether the noun is singular or plural. [5:48]

The difference between something being singular or plural is what we call 'grammatical number' in English. Here's how that idea applies to pronouns!