The verb ser (to be) is used to describe the unchanging characteristics of a person, place, or thing. The list below will help you understand when to use ser (rather than estar ) :

Possession, Personality, Physical Attributes, Profession

El carro azul es mío.
The blue car is mine.

Él es divertido.
He is fun.

Susana es baja.
Susana is short.

Mi padre es un médico.
My father is a doctor.

Date and Time

Hoy es el seis de enero.
Today is the 6th of January.

Son las nueve de la noche.
It is 9 p.m.

Relationships

Ellos son mis padres.
They are my parents.

Rafael es mi mejor amigo.
Rafael is my best friend.

Origin

Ella es de Perú.
She is from Peru.

Yo soy de España.
I’m from Spain.

Yo soy de los Estados Unidos.
I’m from the United States.

Soy de México.
I’m from Mexico.

(yo) Soy de la República Dominicana.
I’m from the Dominican Republic.

Nationality

Juan es peruano.
Juan is Peruvian

Ella es cubana.
She is Cuban.

Note: Words that end in e commonly work for both males and females.

Examples:

Carlos es costarricense.
Carlos is Costa Rican.

Anita es costarricense.
Anita is Costa Rican.

argentino / argentina – Argentinian
boliviano / boliviana – Bolivian
chileno / chilena - Chilean
colombiano / colombiana – Colombian
costarricense – Costa Rican
cubano / cubana – Cuban
dominicano / dominicana – Dominican
español / española - Spaniard
ecuatoriano / ecuatoriana – Ecuadorian
hondureño / hondureña – Honduran
guatemalteco / guatemalteca – Guatemalan
mexicano / mexicana – Mexican
nicaragüense – Nicaraguan
panameño/ panameña – Panamanan
paraguayo / paraguaya – Paraguayan
peruano / peruana – Peruvian
puertorriqueño/ puertorriqueña – Puerto Rican
salvadoreño / salvadoreña – Salvadorean
uruguayo / uruguaya - Uruguayan
venezolano / venezolana – Venezuelan