Третий ребёнок - third child. I figure that it is in education because there's some semblance of theme. Younger people to to school. What else is relevant? Второго сына только третий класс
"The" third child, since there can only be one first, one second, one third, etc. "A" implies one of multiple
I disagree. "a third child" is stressing that he is among the group of all children in families that are the third oldest. Just like it's common to say " I am a middle child" and not only "I am the middle child".
Is this a form of the word три? Or just another word with another meaning, what case is it in?
It's related to три but it's not the same word (just like three and third are different words in English). It's an adjective and here's it's nominative singular masculine (as you'd expect).
I put "my brother is a third child" and it was marked wrong. Is it wrong because of the dash?
"A" in English implies one of multiple. When talking about children and in what order they were born, there can only be one third born child so "The" would be correct
Sorry, I don't agree, Alex. My brother is a second child and so is his wife. Second children have an easier life - I wish I were a second child.
Translation - "My brother is the third child". Just in case any android user is as lost as I was a minute ago.
I typed in "child" for the last word, did not let me write "-ild" and I got it wrong. Update the character limit from 26 to 999 999 999 999 999 000!