Definition:
us is a pronoun used to refer to someone or something that consists of the speaker (first person) and at least one other person (second or third person). It can either be a subject or an object.
Rules:
Us is used for both singular and plural nouns. When used with singular nouns, us is typically referring to the speaker and a group of people around the speaker or even just one person. When used with plural nouns, us is typically referring to the group of people as a whole.
Examples:
1. Us girls are going to the mall later.
2. We need to discuss this between us.
3. Can you help us out with the yard work?
Tips:
When using us as the subject of the sentence, be sure to use a plural verb. Additionally, it is important to note that us is never used to refer to just one person. This would need to be replaced with either I or me depending on the context.