Still struggling with genitive case; why is this wrong: "Ólann sé cupán an chaife"?
That would mean “He drinks the cup of the coffee”.
Not "he drinks a cup of the coffee"?
No — the structure X an/na Y, where X is a noun and Y is a genitive noun, also makes X definite.
So is there no way to say "an X of the Y" in Irish? "A bird in the hand"? "An ace in the hole"? "A man of the people"?
The dative needs to be used rather than the genitive for that structure — éan sa láimh (although the Irish version of the proverb uses éan i do dhorn [“a bird in your fist”]), ás sa pholl, fear den choitiantacht.
I would also like to know this
Where is the "of" in this sentence?
Caife in this sentence is genitive, so its translation is “of coffee”.
But isn't the regular form of coffee also "caife"...?
Yes, it is. Some nouns have identical forms for the nominative singular and the genitive singular.
Namely, those nouns whose plural form is a considered a 'strong' plural.
And is there a visual way to identify a "strong plural"?