Note:  Ser is used to indentify or describe.  It tells what something is, its basic characteristics, or its origin.  Estar is used to tell the location of something or how someone feels.

Uses of Ser

Identify person/object Inherent characteristics or qualities Nationality/Occupation Telling time Express ownership Impersonal expressions Passive voice

El edificio es un templo. La casa es grande. Carlos es pobre. Es carpintero. Son las tres. Los libros son de Juan. Es necesario. El telefono fue inventado por Bell.

The building is a temple. The house is large. Charles is poor. He is a carpenter. It's three o'clock. The books are John's. It is necessary. The telephone was invented by Bell.

Uses of Estar

Location/position Temporary condition/state State of health Form progressive tense

El libro está en la mesa. La ventana está abierta. Juan está enfermo. Miguel está estudiando.

The book is on the table. The window is open. John is sick. Michael is studying.

Common Expressions with "to be"
to be afraid - tener miedo
to be against - estar en contra
to be at fault - tener la culpa
to be careful - tener cuidado
to be cold - tener frío
to be curious - ser curioso (a)
to be happy - estar contento (a)
to be hot - tener calor
to be hungry - tener hambre
to be in a hurry - tener prisa, estar de prisa
to be jealous - tener celos
to be lucky - tener suerte
to be patient - tener paciencia
to be successful - tener éxito
to be thirsty - tener sed
to be tired - estar cansado (a)

Note:  There are two prepositional contractions with definite articles.  A and el combine to form al, and de and el combine to form del.