Updated: Nov 10, 2020
The principal difference is that SER is used in situations that are more permanent - "soy americano" - "I am American". ESTAR is used in situations that are more temporary or changing - "estoy con calor" - "I am hot". As you can see, one is a quite permanent state, while the other is only temporary.
Ser vs estar are similar in meaning, otherwise they wouldn’t be translated as the same verb in English. However, in Spanish, it’s crucial to know to differentiate them because they express distinct ideas that can change the whole meaning of a sentence.
The Spanish Verb Ser
Ser expresses permanent states, the “essence of things,” or the stuff that makes something what it is. You use ser when you want to express who you are, what you do (for a living), and your nationality. In all these cases, you’re describing your permanent qualities as a person that aren’t likely to change.
So, how do you know when to use ser? I’ve written before about the subject and you can read this thorough guide about the uses for these two verbs. Here, I’ll just mention all the situations when you have to use ser:
6. Event location
The Spanish Verb Estar
On the other hand, estar expresses