Estar or ser?
I was wondering, which do I use, when?
The semantic feature of the verb "Estar" is , from its origin , [transient] , while doing "Ser" is [permanent] . This variety of purposes implies a different distribution of the two verbs.
In the constructions with the verb "estar" can not occur adjectives that denote permanent states or derived adjectives psychological verbs describing states or processes with no set time limit, which also denote some permanence. Consider the following examples:
Ele está [estava/esteve/estará/estaria] ingênuo [amado/bondoso/cruel/etc.].
Adjectives : ingênuo (naive) , amado (beloved) , bondoso (kind) and cruel denotes a permanent state, that is, it can not «estar ingênuo há 5 minutos» (be naive for 5 minutes), for example. The property of being naive can not be set in a time interval.
On the contrary , the same adjectives are legitimate in constructions with the verb "ser": Ele é [era/foi/será/seria] ingênuo [amado/bondoso/cruel/etc.].
When we speak of permanent states, we talk about intrinsic properties . For example , an adjective dead does not denote a permanent state , but a state change a transience ( live to dead ) , a result , then , is employed with the verb "estar": Ele está morto. (He is dead.)
And it could be said: Ele está morto há 5 minutos. (He 's been dead for five minutes).
Notice now an intrinsic/permanent property: O carvão é ❤❤❤❤❤. (Coal is black . A Rússia é grande. Russia is great .
being black is a property of coal, and to be great is a characteristic of Russia as being ingênuo can be a characteristic of someone - not a state. Already the following examples denote a state , one transience , not a characteristic property: O céu está ❤❤❤❤❤, vai chover. The sky is black , it will rain. A Mariana está grande, nem parece a mesma. Mariana is great , it does not seem the same.
when temporal expressions as sometimes today, yesterday, etc. appear associated with an adjective, it appears that the tendency is to use the verb "estar", however, not always because adjective properties ( the subject predicate ) largely determine the selection of the copula: Às vezes ele é [amado/bondoso/cruel/etc.]. Ontem ele foi [amado/bondoso/cruel/etc.].
However, when the adjective does not denote any of the permanent/temporary semantic property is the temporal expression that determines the selected verb: Às vezes ele está feliz. Às vezes ele é feliz.
When no time or adjectival element restricts the selection of the word , it can be employed or is to be , although with different meanings: Ele está feliz. Ele é feliz.
Ana Carina Prokopyshyn, https://ciberduvidas.iscte-iul.pt/consultorio/perguntas/o-uso-dos-verbos-ser-e-estar/24877
Choosing between the two Portuguese "to be" verbs is one of the major challenges of learning Portuguese. Many articles, even whole books have been written on the subject. Google turns up some really excellent summaries and it's difficult to recommend just one, but because it is quite concise (and because it adds "ficar" to the mix) you could start with Danmoller's discussion in the Portuguese help index here on Duolingo.
I must admit I sometimes have doubts about the correct choice, but this snippet from an old Portuguese text book (An Essential Course in Modern Portuguese, R. C. Willis, 1971) helps me come to terms with that:
By now the student will probably have experienced some difficulty in choosing the correct verb, ser or estar in a given context. He will have understood by now that ser tells us what a thing is, estar what condition a thing is in. Nevertheless, he will have experienced, perhaps, that some instances seem very borderline or open to more than one interpretation. He should gain comfort from the fact that the situation is flexible and that in a good number of these instances different speakers of Portuguese will probably react in different ways. The problem may often be regarded as possessing a subjective solution. One person may view something as it inherently is (ser); another may gain only a fleeting impression of something and will permit himself to use estar; another may be speaking ironically, and so on.