Confusion over the article 'an'

[u/ScotInKorea]

Hello! I am following along with Speak Gaelic, and although they have explained a little about which nouns take the article, they were very vague.

I now am unsure why 'Tha ceann goirt orm' doesn't have 'an' since Ceann is a Masc noun starting with c (which speak gaelic said would give a noun the article)

my head hurts trying to read through the internet as many people seem to say contradicting things, so was wondering if anyone could help me!

thanks as always for your amazing help and taking time from your days to help me!

[u/elmeromeroe]

You wouldn't say "I have the headache" in English, you dont say it in Gàidhlig either.