"Welcome and thank you, boy."
Translation:Fàilte agus tapadh leat a bhalaich.
This is the vocative - the form used when you address someone. Two separate things are happening. One is that you add a in front, as well explained by bally.baji on this page. This then causes lenition according to the normal rules, so b > bh.
The second is that the i is added to change the pronunciation of the last consonant if all of these apply:
- It is masculine
- It is singular
- It does not end in a vowel
- The last vowel is broad (i.e. a, o, u)
Vocative is a case. There are many case : - - nominative - vocative - accusative - genitive - dative - ablative (I think is like in Latin) In Latin vocative is an apostrophe where you hail a person. I don't know if I was very clear but or else you should watch on Internet. (Excuse me for my English because I am French).
When you're saying something specifically to someone, it is a vocative. Usually, you can tell because the person you're addressing will be at the end of the sentence. And there is an "a" in front of the vocative noun when translated. If the noun is towards the beginning, it's not a vocative. Think of 'a' like using the word "oh". Oh Sister, oh mother, oh brother (where art thou?), etc.
1 exception I've noticed is father. Anything that starts with a vowel will not get an 'a' in front of it, as in athair. And as is the word for professor, Ollaimh, which also starts with a vowel.
It is difficult in a course like this to make you learn both the formal and informal. So they always add an addressee to make it clear.
When it is an older or authoritative person, such as athair or ollaimh, or a plural Anna agus Iain they expect you to use the sibh form.
When it is a first name or a younger person, as here, they expect you to use the thu form. Real life isn't so simple.
Im pretty annoyed at how they have explained this, because "balach" means Boy, and "bhalaich" means Boys. But when im learning "Fàilte agus tapadh leat a bhalaich" the translation on Duolingo says "Welcome and thank you, boy" when it should actually be "Boys" as it is "bhalaich".....
Bhalaich does not normally mean 'boys', although if you have a very good knowledge of Gaelic you should be able to find a situation where it does. I could not find any questions where a word for 'boys' is used at all, but balaich is the normal word.
Bhalaich is the vocative of 'boy' (so used when addressing a boy). You will meet other uses later.
Leat is singular. Leibh is plural/formal. I have explained how to tell which to use in this course above.
More generally you need to read the notes before attempting each section and this may not have been made clear. When you click on an exercise on the web version, you get an option to be taken to the notes. If you are on the app they are not available, but you can get them all at https://duome.eu/tips/en/gd.