When do you use ser versus estar?

A great trick for remembering when to use 'ser' is the acronym DOCTOR. This stands for Description, Occupation, Characteristic, Time, Origin, and Relationship. If you are describing what a person or object is at their core, you use 'ser'. For example, if you say 'Soy estudiante' (I am a student) or 'El cielo es azul' (The sky is blue), you are talking about defining traits. You also use 'ser' to tell time ('Son las tres') and to say where someone is originally from ('Soy de México'). These are things that do not change easily or are considered fundamental facts about the subject.

To remember when to use 'estar', use the acronym PLACE. This stands for Position, Location, Action, Condition, and Emotion. You use 'estar' to talk about where something is physically located right now, like 'El libro está en la mesa' (The book is on the table). You also use it for feelings and temporary conditions, like 'Estoy cansado' (I am tired) or 'La sopa está fría' (The soup is cold). Finally, 'estar' is used with the present progressive tense to describe actions happening right now, such as 'Estamos estudiando' (We are studying). These are all states that can change.

The biggest trap students fall into is thinking 'ser' means permanent and 'estar' means temporary in absolute terms. For example, location is generally temporary, so it uses 'estar' (like 'Madrid está en España'), even though Madrid is permanently in Spain! Another tricky area is that some adjectives change meaning depending on the verb. If you say 'El niño es aburrido', it means the boy is boring (a characteristic). If you say 'El niño está aburrido', it means the boy is bored right now (an emotion). Finally, the location of an event (like a party) uses 'ser', not 'estar'.