El verbo "to be" equivale a ser o estar.

El empleo de uno u otro dependerá del contexto de la frase.

Ejemplos

I am Spanish Soy español

I am tired Estoy cansado

Simple Present

Afrmativo

Forma larga Forma corta

I am I'm

You are You're

He is He's

She is She's

It is It's

We are We're

You are You're

 

They are They're

La forma larga se utiliza en los textos escritos y en el habla formal.

La forma corta se utiliza en el lenguaje hablado y en escritos informales.

Ejemplos

Uso formal Uso informal

I am a student I'm a student Soy estudiante

You are Spanish You're Spanish Eres español

He is sad He's sad Él está triste

She is tall She's tall Ella es alta

It is cold It's cold Hace frío

We are from Málaga We're from Málaga Somos de Málaga

You are nice You're nice Sois agradables

They are policemen They're policemen Son policías