"I am a child."

Translation: Eu sou uma criança.

[CarlosMora11]

Could be "Eu sou um menino" ?

[jenlawson]

Still confused about sou/estou. I thought estou was used in unchanging situations, but presumably, one will not remain a child forever?

[frozen3v0lution]

Would "um filho" not work here as well?

[Paulenrique]

Yup, it works but as there's not context,a bit strange for us...