"My sister is old, but I am young."
Translation:Minha irmã é velha, mas eu sou jovem.
why is this ser and not estar? I was using a rule was "ser" for permanent, "estar" for temporary. I'm not always going to be young, it's a temporary condition. I think I need a more subtle rule than the one I'm working with. For example, I now am not sure what to say for "my sister is thin but I am fat", would it be "minha irma esta magra mas eu estou gorda" or would I use ser there too? You can't change weight very fast. What about alto and baixo? You don't usually change height after adulthood.
In some cases it is a case of point of view. To be young = it continues through a long time. That's why we say "eu sou jovem". Eu estou jovem = I feel young. But, again, it's a matter of choice:
- eu ainda sou jovem = eu ainda estou jovem.
- eu sou magro (I am thin)
- eu estou magro (I am thing, but I can get fat)
- eu era/estava gordo, mas agora sou/estou magro - do you notice how ser and estar can be interchangeable in these senses?