why does coch mutate to goch here?
sgert is a feminine noun and so the adjective mutates accordingly.
Will there be a way to know which nouns are feminine in course updates? It seems like I only find out which are feminine by looking out for the mutations.
That's pretty much it! The other thing to look for is a soft mutation (treiglad meddal) when the word follows "the": Single Females Mutate"
gardd -> yr ardd
cath -> y gath
Of course that won't help with sgert, which can't mutate :o)
If you look in the discussion ‘Additional Resources’ you will see some links to some on-line and paper dictionaries. There is also a good smart phone dictionary app, ‘Ap Geiriaduron’. Those will all show you the genders of nouns.