The business of "dw i'n siarad" versus "siaradaf" is a bit more complicated than Alxmrphi’s post makes out
Yes,
siarad is a verbal noun, but the fact that siarad stays the same in constructions such as “Dw i’n siarad” is not related to the fact that siarad is a verbal noun -
bod is also a verbal noun, but "bod"
does change in the construction "dw i'n siarad". So, I'll explain why.
First of all, in Welsh
all “verbs” are actually “verbal nouns”. So,
bod, rhedeg, neidio etc are all called verbal nouns, unlike the English
to be, to run, to jump which are all called “verbs”.
Welsh verbal nouns can be conjugated – “conjugate” simply means giving the different forms of a verb, making it obvious who the person is, what the tense is etc (je parle, tu parles etc). So, with “bod” you can conjugate in a few different ways:
rydwyf i (I am, formal),
rwy (I am, informal, southern dialect), or
dw i (I am, informal, northern dialect). Some conjugations are more formal than others – rhedeg, siarad, neidio etc all conjugate quite formally to “rhedaf, siaradaf, neidiaf”, none of which are used in spoken Welsh.
So, to get back to “dw i’n siarad”! The reason siarad stays the same here is because this type of construction is what is called a “
periphrastic construction”. It might be easier to understand if I use the Welsh grammar term - in Welsh, it’s called “ffurf gwmpasog y ferf” (cwmpasog = mynd o gwmpas = the “roundabout” form of the verb).
If you want to be concise, you use “ffurf gryno y ferf” (the “concise” form) which is “siaradaf”. If you want to “go around” this, you can instead use the roundabout form and use the longer construction “dw i’n siarad”.
In the case of “dw i’n siarad”, this phrase is made up of the verbs
bod + siarad. Bod here works as an auxiliary verb, which is also called a “helping verb”. You use the helping verb to help specify the person and the tense, so that you don’t specify that directly using “siarad”.
So, periphrastic construction (ffurf gwmpasog) = dw i’n siarad (and this is a lot more common in spoken Welsh)
Concise construction (ffurf gryno) = siaradaf (and this is only used in more formal, written Welsh)
Moving on to the next point:
I found
hail in Geiriadur Prifysgol Cymru.
tau appears in the GPC and also on the website geiriadur.net. Again, I never said that these words were used in the modern spoken language, but doesn't the fact that they're in the GPC mean that they have some level of existence in Modern Welsh?
No, the fact that a word is in GPC does not mean it is used in modern Welsh. GPC is a fabulous resource, but it notes all words which have been recorded in the Welsh language, dating back a fair few centuries! There are a huge number of words in it which people today have never heard of. They would not be used in modern Welsh, and you really would have to look them up to have any idea what they were. As a beginner Welsh student, you would be better off using Geiriadur yr Academi instead, which contains a lot of more modern Welsh
