Verb to be (Present)

It is the most used verb and also the most important, it allows us to say when a subject is in a certain place, to describe or how it feels.

                               +                                                  -                                                  ?

I am = I'm                              I am not = I'm not                             Am I...?

            (singular) You are =  You're             You are not = You aren't                    Are you...?

He is = He's                           He is not = He isn't                        Is he...?

She is = She's                        She is not = She isn't                      Is she...?

We are = We're                      We are not = We aren't                    Are we...?

                (plural) You are =  You're              You are not = You aren't                  Are you...?

They are = They're                They are not = They aren't               Are they...?

It is = It's                                It is not = It's not                             Is it...?

Affirmative:

She is my sister.

He is my brother.

They are my friends.

We are in the park.

I am in the hospital

You are at home

Negative:

She is not my sister.

He is not my brother.

They are not my friends.

We are not in the park.

I am not in the hospital.

You are not at home.

Question:

Is she my sister?

Is he my brother?

Are they my friends?

Are we in the park?

Am I in the hospital?

Are you at home?

Here two videos.

Some exercises: 

Matias ____ my best friend.

They ____ men.

She ____ at home.

Carla and Diego ______ at University.

My pet _____ happy.

Paty and I ____ sisters.

We ____ in the restaurant.