“na” - is the “than” here and before a vowel it acquires a “g”. It crops up in the “mwy … na” for “more than” types of expressions. It’s not the colloquial “nag”, that people down south use, for the strictly correct “nad”, that was discussed elsewhere recently.
The subtitles look like a very loose translation, I haven’t seen the program - is it a maths program? Are we ready to share (or divide or is Rhannu just the name of the game?)?
It is properly written… 
…literally the subtitle means we are ready to divide
( Dan ni is one of the squillions of variants = yn ni in the southern course )
Rich 
It’s a quiz programme that divides 16 contestants into 2 teams of 8, then those 8 into 2 teams of 4, then those 4 into 2. The first series has just ended but some of the episodes will still be available on clic and iPlayer. We’re currently looking for contestants for the next series!
no, this is a different nag to the one that varies between nag and nad! This one (meaning ‘than’) is always nag before a vowel (na before a consonant).
I sort of remembered seeing a thread about nad recently, and wanted to check it out first, but I couldn’t find it (but now I see it was a different one anyway!)
As for Rhannu…@siaronjames explained it better than I could possibly do, so I can just add it’s interesting for me because the language is pretty easy and the questions are about Wales so I can learn something at the same time! 
Oh really? 
I’m happy to hear it, then! 
(thanks everybody for the answers)
I’m glad you liked the questions. Some of them were mine!
I ended up listening to the whole lesson in the car and it’s really interesting that the lesson also has “it’s a big world, but we can’t change it” using "ond nag yn ni’n gallu ei newid e.
Same lesson but two different" nag yn ni" constructions. I don’t know if that was deliberate?
I don’t know either, but I wouldn’t rule it out! 
Yes, to me it seems like there is a lot of that using different types of ‘have’ and different types of that - too much of a coincidence for me!
Rich
Well that’s the thing (dyna’r peth) or as Tommy Cooper might have said if he spoke Welsh:
Jyst fel na!
or something like that
neu rhywbeth tebyg i hynny
Heard a track I rather liked – English-language, but band from Rhondda Cynon Taf – on Radio Cymru, & tweeted about it. Got a response from the band which said llwyth o ganeuon ar y gweill – a load of songs on the – what!? Everything I look up says that gweill is something to do with knitting-needles! Is this a Welsh-language autocorrect from a typo for gwefan, or am I missing something about gweill?
ETA: Or does it mean – having looked at the website and not found a load more tracks – that they’ve got more tracks nearly ready to release – just, kind of, still on the needles, not yet sewn up and ready to wear?
According to good old unreliable google translate, it means; ‘in the pipeline’ or in progress’ which I have to say, sounds about right in this instance. 
Yeah, I’d just about got there – didn’t think to try Google Translate! – but nice to have the belated hunch so quickly confirmed
Yeah, it is a bit of a stretch, but if you think of a knitting project being worked on you’d say it is “on the needles” so I would guess that’s where the phrase comes from. (gweill is the plural for “knitting needles”)
E2A - and I just found in my app that a “project in development” is prosiect ar y gweill
Shared by Joe on Twt:
https://toot.wales/@Joe/102032211101318262
Pumdegau
Chwedegau
Saithdegau
Wythdegau
Nawdegau
Err
Dimdegau
Degdegau…?
Any comment please?
ooh - good question! Not sure on ‘official lines’, but I know the Estella song “Dw’ Isio Byw yn y Saithdegau” refers to “Dimdimau” for (20)00s. Trying to think what I’ve heard for (20)10s, but nothing springs to mind (probably just washed over me). Nearest I can think of is “Dwy fil degau”, but having said that, I don’t see why Dimdegau and Degdegau wouldn’t work!
Just an idea… what about “undegau” instead of degdegau?
In English we’d say the “nineteen-tens” or the “twenty-tens”. Somehow “the tens” doesn’t work on its own like the twenties, the thirties, etc. So I’d probably say “yr ugaindegau” myself. I’ll have to listen out for what others say. Being a weekend, I’m not in the office, otherwise I’d throw the question at my colleagues!
I’m making these up -
As the date decades seem to mirror personal ages (twenties, thirties, etc) how about arddegau for 2010’s?
And drwgau for the naughties