Continuing along my "to be" theme, today I am going to discuss the difference in Spanish between ser and estar, both verbs with mean "to be".
The Spanish verb ser indicated permanence. You choose this verb any time you want to discuss "being" something, somewhere, or someone that will not change for a long time, or ever. This is appropriate for a career, for a physical characteristic or personality trait, a nationality or religion, for time, or for the time or location of an event. For instance:
Él es médico. - He is a doctor.
Mi amigo es ruso. - My friend is Russian.
Yo soy alto. - I am tall.
Son las tres. - It's three o'clock.
Tú eres hermosa. - You are beautiful.
El partido es el viernes. - The party is on Friday.
All of these traits are permanent, and unlikely to change.
The Spanish verb estar indicates a more temporary condition. This is the verb to choose when discussing a temporary feeling, mood, physical condition or characteristic, a geographic location, or with a gerund to describe the present progressive tense.
Estoy enojado. - I am angry.
Ella está cansada. - She is tired.
¿Por qué estás en mi dormitorio? - Why are you in my bedroom?
México está al sur de los Estados Unidos. - Mexico is to the south of the United States.
Maria está escribiendo. - Maria is writing.
In these examples estar is used to describe temporary conditions, locations, and ongoing actions.