"Tea and coffee! Thank you, friend!"
Translation:Tì agus cofaidh! Tapadh leat a charaid!
Why is if sometimes leat and other times leabh? It doesn't seem to reflect formal and informal or coming before a vowel or consonant. Help! Am I missing something?
When you are talking to someone starting with a consonant, you add a in front. It's a bit like saying oh friend in English. This a causes lenition (i.e. adding an h after the majority of consonants). ch is usually pronounced as in loch or dreich or German Bach 'stream' or ich 'I'. But in some dialects it can be very mild, sounding, in the extreme, like h. This is most common in Ireland, or in Scotland near Ireland (e.g. ann an Ìle = in Islay). Quite a lot of issues covered all together but I hope it helps.
We don't say that one pronunciation is 'properer' than another, but the most common in Scotland is like the ch in loch or Bach. If you are not familiar with this sound you will have to listen to the examples but it is like a /k/ while letting the air leak out instead of completely blocking the air flow.
Dialect. I had never actually heard "ay-us" before using Duolingo but it is clearly dialect from somewhere. "G" does have a propensity to change into "y" as is shown with lots of English words with a "y" that correspond to other words with a "g":
day cf. German Tag
yard cf. garden
Also "g" is sometimes pronounced as "y" when it is lenited.
So g → y is quite common across languages.
Because it is tì not ti. Almost impossible to see the difference on many screens but there is in fact a grave accent on the i. You could try zooming in or increasing font size as that may help.
Most people agree that Duolingo made about the worst font choice they could have done on a language-teaching program. It's even worse on the discussion page than it is on the question page.
Duolingo does not normally object if you get an accent wrong, but for some reason it does sometimes in Gaelic.
The accent makes the vowel long so ti would be pronounced as in French (if this word existed in French, but rhymes with si ). There is no exact equivalent in English. Like tip is a vague approximation, but like tea with a short vowel is a better description. But tì is an approximation to English tea.
Edited: The only correct form in this sentence is a charaid. This is the vocative form of the noun (the form used when addressing someone) (no change in this example) and the vocative particle (a) which you put before a name starting with a consonant when talking to them, which causes the lenition.