"You are only girls."
Translation:Níl ionaibh ach cailíní.
I have just had an exercise which said: Níl iontu ach dlíodóirí and Níl ach dlíodóirí iontu are correct translations for : they are only lawyers. But in this sentence I have to put ionaibh between níl and ach. Is there a rule or a time that implicates the word order? Go raibh maith agut
That is a literal translation. Irish is not English, it uses different constructions. Tá tú fear is a big no no in Irish. Tá (pronoun) (noun) is incorrect in Irish. The nearest you can get is Tá tú i d'fhear, tá tú i do chailín etc., although it's more common to say Is fear tú, is cailín tú.
Níl ... ach = except, only. So if you say Tá sibh i bhur gcailíní then you can say Níl ionaibh ach cailíní although I don't think the cailíní would be pleased about it.
Notice the connection between "i" and "ionaibh", i (sibh) = ionaibh.
One might expect the use of "ní" here, rather than "níl" as per https://www.duolingo.com/comment/23725733/N%C3%ADl-rogha-agat. What's the logic?