Differences between languages are or become differences in the worldview and thinking logic of their speakers. Between English and Spanish, one of the most important differences is the verb “To Be” which translates into Spanish sometimes as the verb “Estar” and other times as the verb “Ser.” How to recognize, with the logic of an English speaker, when to use one or the other.
The difference between “Ser” and “Estar” is not very clear even for Spanish speakers. It is common to say that “Estar” is for changing conditions and “Ser” is for permanent conditions. But we say “Él está muerto” (He is dead) and “Ella es estudiante” (She is a student) and nothing looks more permanent than death, and we are students to be something else, not to stay as a student.
A better way to understand the use of both verbs is to think that “Estar” is for conditions and “Ser” is for identities. “Yo soy Luis y estoy feliz” (I am Luis and I am happy.) My identity and my actual condition, my “Ser” and my “Estar.” That way, we can understand why is “Él está muerto” and no “Él es muerto” and why is “Ella es estudiante” and no “Ella está estudiante.”
Other Uses
“Ser” and “Estar” have other uses in Spanish. “Estar” indicates location or position. “Yo estoy en mi casa”, “Nueva York está en Estados Unidos” (I am at my home, New York is in the United States.) When used with the gerund form, “Estar” forms the equivalent of the present progressive in English. (“Tú estás corriendo”, You are running.) “Ser” helps other verbs to form passive forms. (“El ganador fue premiado con un trofeo”, The winner was awarded with a trophy.)
Difficult cases
Sometimes, an attribute can be used with “Ser” and “Estar.” For example, you can say “Tú estás loco” and “Tú eres loco” (You are crazy and You are crazy.) And as crazy as it sounds in English, there is a difference: When you say “Tú estás loco,” you are implying the other person has a condition that doesn’t let him or her being in their better judgment, doesn’t matter how long that condition last. When you say “Tú eres loco,” you are saying that craziness is a personality staple of the other one. Same as “Yo estoy triste” and “Yo soy triste” (I am sad and I am sad.) Because of something that happened, “Yo estoy triste,” but if “Yo soy triste,” then sadness is part of my being and that is so sad that it is very uncommon to hear it.
There are many cases and situations where doubts about which one is more appropriate will arise. If you keep in mind that “Ser” is for identity and “Estar” is for condition, you will be able to resolve most of the situations.