Okay and why is there a 'h' before ull? M'húll?
There isn't a "h" before "úll", except after "a" when it means "her" ("a úll" - "his apple", "a húll" - "her apple").
(There are a few other grammatical circumstances that trigger a h-prefix, but "mo" isn't one of them).
If Mo ull and m'ull is both 'my apple'. Why is mo ull wrong in this sentence?
Because mo úll is wrong. When mo or do come before a word with a vowel (or f+vowel), they drop the "o" and are written with the word. mo úll because m'úll. mo fear becomes m'fhear.
When 'do' contracts it can become d' or t'
'd'úll' or 't'úll' for 'your apple'.
D'úll is right--not t'úll because it's the contraction for DO úll
t'úll is also correct as it has been said and written by native speakers for four hundred years. Writers like Peadar Ua Laoghaire and Mairtín Ó Cadhain wrote t'úll.
I didn't know that--thank you! ( I must also be reading the wrong authors.)
Oh d'úll is correct too, they both are. An seabhac, Tomás Ó Criomhthain would have also used t'úll, as did Séamas Ó Grianna. Many of the great modern authors did.
Did you mean "mo úll becomes m'úll"?
'Mo' and 'do' become m' and d' before vowel, so, yes, m'úll is correct.
Will learning the Irish alphabet, consonants and vowels help with lenition and eclipsis?