Sure this would’ve been asked at some point but it’s hard to search for.
I did Old Course North 1, and we’d say “Nes i siarad o” or “On i’n licio fo” etc.
Now I’m doing New Course 1 and it’s “Ti’n siarad hi’n dda iawn”.
I vaguely remember “o/fo” is for intangible nouns? Is that right? Am I wrong to say, “Dw i ddim yn siarad o”?
It’s a gender difference. O/fo is masculine, hi is feminine. I assume that the language the other person is speaking well is feminine to make it hi.
Yeah, the “hi” refers to Cymraeg/iaith which according to the geiriadur is feminine so that makes sense. Thank you. If I don’t know the gender, would o/fo be a safer bet?
So I guess I’m at the stage where noun gender matters. Oh, joy 
Percentagewise yes - there are more masculine nouns than feminine ones 
That’s going to come in very helpful! My hands are already full with the treigladau without stressing over noun gender which is something I still mess up in Spanish after 15 years!
Given that some nouns can be either, in the scheme of things, it’s one of the smallest to worry about
It depends how correct you want to be. Dw i’n licio fo is frequently heard for even feminine things, like a language. Dw i’n siarad o is possible in everyday speech.
Gender can be more fluid in Welsh than grammar books generally suggest.
Even in formal grammar, although languages are feminine, it is correct to say ‘Cymraeg da’, i.e. the adjective does not mutate after language names.
The same is true of ‘Nos da’ of course.
But if you’re referring to natural gender you would distinguish between Dw i’n licio fo (I like him) and Dw i’n licio hi (I like her).
Good to know. At least it’s not like eg Spanish where if you get the noun gender wrong you risk turning it into a totally different word!
Welsh has one very common word like that - gwaith - when it’s masculine it means the noun “work”, - dw i’n mynd i’r gwaith “I’m going to work”, but when it’s feminine it means “times” as in unwaith, dwywaith, tair gwaith - once, twice, three times
I think that can happen in Welsh, too. Gwaith means ‘work’ when it’s masculine but ‘time’ when it’s feminine, e.g. dwywaith = ‘twice’ (two times).
I have always been amused by the difference between el papa and la papa - the pope and the potato!
Indeed, and another factor adding to that percentage is that loanwords tend to be adopted as masculines.
Unless of course they look obviously feminine like lori.
Obviously.
Being a geordie who lives in Cornwall i struggle with English most of the time