Learning how to use the apostrophe S in English helps you answer one simple question with confidence: who is that? If you are an ESL beginner working through family vocabulary, this lesson shows you how to talk about relationships, belongings, and connections using words like cousin, brother, father, and grandmother.

The idea starts with a family tree, that picture full of cousins, brothers, sisters, mothers, fathers, and grandparents. When you point to someone and ask who is that?, you can answer with a possessive: she is my cousin's best friend. That little apostrophe plus S does a lot of work, and here we break down exactly how.

What does the apostrophe S mean in English?

The apostrophe S ('s) shows a link between two things. It is small, but it changes the whole meaning of your sentence.

According to the lesson, you use it in three situations [00:52]:

• To express that something or someone belongs to a person.
• To express that something or someone is connected to a place.
• To show the relationship between two people.

What is the apostrophe S used for? It shows possession, connection to a place, or a relationship between people. Example: she is my cousin's best friend shows a relationship.

Each use answers a different question, but the form stays the same: name plus 's.

How do you show possession and place with 's?

When something belongs to a person, you attach 's to that person's name. Take the sentence where is Lucy's book? [01:28]. You are not asking about any book, only the one that belongs to Lucy.

For a connection to a place, the example is Arnold's school is across from the store [01:47]. Here 's tells you which school matters: the one Arnold goes to.

And for relationships between people, listen to Kelly is my brother's swimming coach [02:14]. That 's explains exactly how Kelly and my brother are linked.

When do you put the apostrophe after the S?

Here comes the part that confuses many learners. With regular plural nouns, the noun already ends in S, so you do not add another one. You just add the apostrophe by itself [02:37].

Look at these family examples:

• My brothers' toys are on the floor [02:56]. More than one brother, so the plural already ends in S.
• My sisters' English teacher is kind [03:14]. Again, plural sisters, so only the apostrophe goes after the S.

Do you add an extra S to plural nouns like brothers? No. If the plural already ends in S, you add only the apostrophe: my brothers' toys, not my brothers's toys.

After that rule, notice the pattern: singular gets 's, and regular plurals ending in S get just the apostrophe.

How do you use apostrophe S with family members?

This is where the lesson really connects to everyday speech. You can point at a photo and describe both the person and their belongings.

• That's my father's laptop [03:52]. The laptop belongs to my father.
• That is my sister's car [04:12]. The car belongs to my sister.
• They are my friend's children [04:26]. The 's after friend shows the relationship.

And then something interesting happens. You can stack two apostrophe S's in one sentence: those are my friend's children's toys [04:38]. The first 's connects the children to my friend, and the second connects the toys to the children. Two links, one clean sentence.

How do you complete sentences with the possessive S?

The best way to lock this in is practice. The lesson offers three fill in the blank moments where you decide where the 's goes [05:12].

1. The clothes belong to my brother, so: my brother's clothes are very elegant.
2. The hat belongs to my grandmother, so: my grandmother's hat is pretty.
3. The house belongs to Sally and Emilio, so: this is Sally and Emilio's house.

That third one hides a key rule. When two people share one object, you add 's only after the last person mentioned [06:20]. So it is Sally and Emilio's house, not Sally's and Emilio's house.

With these patterns, you can now answer who is that? and describe what belongs to whom using your own family. Try writing three sentences about your relatives and share them in the comments. Which one felt trickiest to build?