There are two different forms of the verb “to be” in Spanish: ser and estar. If you do accidentally choose the wrong one, chances are you'll still be understood. There are a few instances, however, where making the wrong choice can change the meaning of your statement — sometimes in a rather embarrassing way. It can mean the difference between saying someone is good — Carmen es buena — and saying someone has a “good body” — Carmen está buena. Ladies, if you're walking down the street and hear someone yelling, “¡Ay, mami, qué buena estás!” he doesn't mean you look like a nice person. He's using a piropo, which translates as “compliment” but may feel more like a catcall.
SER: to be
Not sure when to use ser and when to use estar?
Keep this in mind: If it's something more or less permanent, like birthplace, nationality, or a physical characteristic, use ser. If it's something that changes, like being tired or hungry or lost, use estar.
yo soy (soy)
tú eres (EH-rehs)
él, ella, usted es (ehs)
nosotros somos (SOH-mohs)
vosotros sois (soys)
ellos, ellas, ustedes son (sohn)
ESTAR: to be (located)
yo estoy (ehs-TOY)
tú estás (ehs-TAHS)
él, ella, usted está (ehs-TAH)
nosotros estamos (ehs-TAH-mohs)
vosotros estáis (ehs-TAHYS)
ellos, ellas, ustedes están (ehs-TAHN)
Choosing between ser and estar trips up a lot of people, but it doesn't have to be complicated if you know the basics. The verb ser is used to express the following:
• Nationality, origin, or a permanent characteristic:
Soy americana. I'm American.
Jennifer es de Inglaterra. Jennifer is from England.
Juan es bajo. Juan is short.
• A characteristic or condition that will probably be the same for a long period of time:
Ellos son abogados. They are lawyers.
• Date and time:
Mi cumpleaños es el veinte de agosto. My birthday is August 20th.
Son las dos. It's two o'clock.
The verb estar is used to express the following:
Estoy aquí. I'm here.
El coche está en el garaje. The car is in the garage.
• A temporary condition:
Linda está cansada. Linda is tired.