Thanks, Richard. That’s very clear.
I was fairly sure that the y in the middle would always be right, but sometimes rules are emphasised for beginners for ease of learning, and it turns out later on that there’s some flexibility for reasons of style / nuances of meaning, once you know what you’re doing. I wondered if this were one of those occasions.
Thanks again!
Good point - “We’ll encourage you to say it the normal way” vs “This is the only possible way.”
I originally included “the church tower” as an example because it’s one I use when I’m trying to tell adult English learners the difference between nouns and adjectives - the church tower, the tall tower, this tower is tall, but not *this tower is church. I got rid of it, because it didn’t help - but then I realised that it could actually be useful.
So the Welsh actually corresponds very closely to the English: Mab brenin ydy tywysog; mab y brenin; tŵr yr eglwys; y car rali.
Of course, there are cases which aren’t so clear - and in those instances you’ll see native speakers hesitate or ask for help; but the basic principle is there.
A good way of putting it!
In the back of my mind (vaguely – you’ve made me think about it more…) was the possibility of swapping the possessive with an extended noun phrase as adjective as we sometimes do in English for emphasis or stylistic effect.
We do that for stylist effect – it’s unusual but not grammatically wrong and I wondered if Welsh had similar stylistic licence in this sort of situation (the general principle, not necessarily explicitly for this phrase, of course).
There’s one thing that’s important in Welsh, (which is not in English), and that’s the difference between the specific and the general. It comes up in a number of Welsh constructions, including ‘the’, ‘in’, the possessive, ddim/mo and more.
The definite article
cath - a cat, any cat, it’s not specified which cat
y gath - the cat, ie that specific cat that I am talking about
Yn and mewn
mewn trefi ar draws y wlad - in towns across the country, any towns, doesn’t matter which
yng nghanol y dref - in the town centre, and we’re talking about a specific town here
Possessive
wisgers cath - a cat’s whiskers
wisgers y gath - the cat’s whiskers (the whiskers of the cat)
Days and nights
dydd - a specific day, such as dydd Iau, dydd Nadolig
diwrnod - any day, perhaps a diwrnod diflas, a miserable day
nos - a specific night, nos Iau, nos Galan
noson - any old night, noson wyntog, a windy night
Ddim and mo
Ddim is used with non-specific things.
Mo is used with specifics, eg people, places, the definite article, possessive pronouns, pronouns, this/that, etc.
Welodd o ddim cath - he didn’t see a cat
Welodd o mo’r gath - he didn’t see the cat
Welodd o mohonon ni - he didn’t see us.
I honestly hadn’t put this all together until I did the Sadwrn Siarad the other week, and our tutor, Karen, went through ddim vs mo in detail, which was super useful.
In English, it really doesn’t matter whether something is specific or not, it doesn’t really change anything. In Welsh, it does matter, but we’re not used to looking out for it, so we don’t always spot it.
Are there any other situations where the specific and general are treated differently? I might have to add this as a cheat sheet to my website!!
Could someone help, bore became fore after ysgol is that because y is a welsh vowel?
No, nothing to do with y or vowels.
As I don’t have the full sentence/context, I’m guessing it’s probably because time adverbs (like those that tell you “how often” or “when”) have a soft mutation, e.g. aeth o i’r ysgol fore ddoe = he went to school yesterday morning.
The other possibility is that fore is describing the school and adjectives have a soft mutation when they follow a feminine noun (school is a feminine noun), e.g. aeth o i ysgol fore = he went to a morning school.
That’s assuming you haven’t mistaken 'fory (tomorrow) for fore, e.g. mae o’n mynd i’r ysgol 'fory = he’s going to school tomorrow.
It’s maybe even more off topic than the whole “meals in Britain” issue 
- but I hope you don’t mind.
I saw the example above, just slightly changed, in the lyrics of a song called “Kneel, Mulholland: Drive!”. It seemed a bit weird, but funny and fit the style of his lyrics so I didn’t consider it could be some sort of quote!
The coincindence is that the song is by the guy who introduced me to Datblygu and, as a consequence, to the Welsh language.
@David_B
In any case, in this debate about meals it’s interesting for me to notice that the standard Welsh sequence brecwast-cinio-swper always seemed just a perfectly normal translation of our current most common standard colazione-pranzo-cena (vs the now rarely used posh/formal “prima colazione - colazione - pranzo”).
It is true that cinio sound more like cena.
But I have also heard (and see it confirmed on the dictionary) that cinio in Wales is more commonly used for midday, but really is the equivalent of “a main meal” and sometimes it’s also used for the evening.
This also matches the Latin cena as main meal. So the Welsh it’s all logical to me, unlike the English! 
p.s. just to close my Sunday morning ramblings, I’d say that in English class we were taught “breakfast - lunch - dinner - supper” (with us all wondering why would they need to eat twice every evening).
Then first time in the UK, in my host family in Whitley Bay we had “breakfast - lunch - tea - supper” I’m not sure I’ve ever heard of a midday dinner until…now! 
They say it’s regional.
It might be, but my mother’s family is Scottish, her parents moved first to Yorkshire then Sussex, and my father was born in the Greater London area, mostly raised in Sussex, and then joined the Royal Navy, living in Gosport, Plymouth, and Helensburgh. I frequently have absolutely no idea where the phrases I say “belong”. So while I’ve tried to stay consistent in learning South Welsh, and stick to Ceredigion regionalisms where given options, I really don’t worry too much if I learn a word in isolation from the television or radio or someone in my chat group, and it turns out to be more North or East. The mix of words we use tells a sort of story of where we’ve been and who we’ve known and learned from. I like that, even if the result is mildly chaotic.
– ◡ ◡ | – – | – || ◡ ◡ | – – | – ◡ ◡ | – –
– ◡ ◡ | – – | – || – ◡ ◡ | – ◡ ◡ | –
Looking stuff up online reveals that this is apparently an example of an “Elegiac Stanza”: [t]he Elegiac Stanza differs widely in character from hexameter verse (of which it is a mere modification) by its division into Distichs, each of which must have its own sense complete. It is employed in a great variety of compositions,—epistolary, amatory, and mournful,—and was especially a favorite of the poet Ovid.
You learn something new every day
True!
And starting from a question about lunch in Welsh, you can find yourself learning something about Elegiac Stanza and Ovidio - go figure!
My favourite quotation about feet and meters is from Pope’s Essay on Criticism:
A needless Alexandrine ends the song,
That, like a wounded snake, drags its slow length along.
The joke being, of course, that the first line is Pope’s standard honest to goodness iambic pentameter of ten syllables and the second the highly suspect French Alexandrine which goes on and on and on for twelve.
Massive bunch of nerds here. 
I resemble that remark!
I saw a good explanation about i’w, I have listened and listened but it’s said so quickly I just don’t seem to be able to catch what it sound like.
I did see a question like this about another word, someone was kind enough to suggest a word and then take something off the beginning.
It’s so small, but annoying.
Ta
Shwmae pawb!
I just got to “Es i mas” on automagic and it threw me off a little because I’m sure it should be “Es i fas” because ‘Es i’ triggers a treiglad meddal. So the question is, why does SSiW say “Es i mas”?
Diolch!
Occasionally you get situations where a word ‘resists’ mutation. Mas is one of those. It just tends to stay as mas no matter where you use it.
Diolch Deborah, rwyt ti’n ddefnyddiol iawn! One more quick question, is this a case where some regions mutate where others don’t? In my Dysgu Cymraeg book mas is mutated in phrases like tu fas i.
Ah yes, it’s fas in the set expression tu fas i which is stating a place, rather than a movement towards ‘outside’, so you get es i mas a nes i sefyll tu fas i’r tŷ - “I went out/outside and I stood outside the house”.
GPC compares mas with i maes (and similar expressions in Cornish, Breton and Irish), so it’s literally more or less the same as English ‘afield’ (on felde, in a field). I’m guessing it’s the vanished i that protected it - but with no i in tu **i mas, it’s exposed to the full force of tu…
Cwestiwn am ‘mor’
First two phrases are from the Sylfaen coursebook, the last is pulled from a dictionary.
My question is, why do we need to use the definite article with the last phrase, when it isn’t used in the second? i.e. Why is it not “mor ddu â brân” for as black as a raven?