Como vimos en la sección de Vocabulario, el verbo ‘to be’ se utiliza con un adjetivo para decir cómo estamos. Mira los ejemplos:

I am worried about my Math exam (exámen de matemáticas)
You are sleepy, go to bed now! (véte a la cama)
He is happy / the boy is happy
She is sad / the girl is sad

Ahora mira lo que pasa cuando tenemos varias personas:

We are worried about our Math exam (exámen de matemáticas)
You are sleepy, go to bed now! (vayan a la cama)
They are happy / the boys are happy
She is sad / the girls are sad

To be
Singular		Plural
I	am	We	are
You	are	You	are
He/she/it	is	They	are