What does the "Dentals" rule apply to?

Féach an nóta a thug mé ar snath eile.

When you have to stick a "h" on a word, you don't do so for the letters:

d t s

if they're preceeded by d t s l n.

This rule is known colloquially as the "dots after dentals rule".

Examples:

an duais
don seomra
seandoctúir

One also you'll come across (which is irregular), is that no form of the verb "abair" gets a séimhiú:

Ní dúirt
Ní deir, ní deireann
Ní déarfaidh

Also you don't stick a séimhiú on "gach" ever:

ag iarraidh ar gach duine

And you don't stick a séimhiú on an "f" after "gan":

gan fear (but "gan chos, gan bhac, gan bhean")


Also I think there's something about not séimhiú'ing a "b" after an "m": um bosca, ach um gharda

There's a few more I believe...

Thanks, FnaMb....I don't have my books with me and couldn't really call this rule to mind. I had the general "gist" of it but not well enough to try and explain.

Your description is perfect...very helpful and relatively easy to put into the "mental hard-drive".

Le meas,

James

Great explanation!

Right but when 'ar' comes into the equation there is a h
ar dhaoine mar shampla? Ni bhaineann se sin leis an riail? An bhfuil sé sin ceart?

Here's how your thought processes should work:

Step 1:
Does the thing we're working with cause a séimhiú? We're working with "ar", so the answer is Yes.

Step 2:
Does the next word start with a D, T or S? If not, just go ahead and stick a séimhiú on it. But if it does start with D, T or S, move on to Step 3.

Step 3:
What is the letter behind the D, T or S? Is it one of the following: DeNTaLS? If so, then don't stick a séimhiú on it; otherwise go right ahead.

So we have the following:

ar bhuachaill
ar gharda
ar dhuine
ar throdaí

don bhuachaill
don gharda
don duine
don trodaí

Note that "sa" gets lumped into the same group as "don" and "den":

sa bhuachaill
sa gharda
sa duine
sa trodaí

You're right in thinking that there's no reason why there shouldn't be a séimhiú on the last two... there just isn't!

So I wasn't thinking strangely then.. I suddenly felt after all my years of Irish that I was awful!!:)
Thanks

Tá fáilte romhat a chara.

sa duine
sa trodaí

You're right in thinking that there's no reason why there shouldn't be a séimhiú on the last two... there just isn't!

I suppose it's because "sa(n)" = "s"+"a(n)"
Strangely enough, in this case, when the "n" is not pronounced, it's not written. But since it was there, it explains why there's no séimhiú...

The longer form "ins an" is still used in spoken Irish in some parts, and in the written language. Bainimse úsáid as uaireanta.

By the way, "sa" doesn't not uniformly cause lenition amongst dialects, but also eclipsis (at least in Cois Fhairrge, cf Learning Irish).

I just noticed the typo above. I still could re-edit the post, but I'll leave it this way: it makes me think of the French negation...

the lack of lention on the dentals may be down to the unstableness of d and t in most dialects once the dental fricatives had been displaced or just that lack/less mutation of d anf t occur due to over generalisation.

Remember, sometimes there are psychological, social or physical reasons for language change, not just grammatical

Just so you know, it's only "san" before vowels:

Bhí sé sa pháirc.
Bhí sé sa bpáirc.
Bhí sé san fharraige.
Bhí sé san áit.

This is a very important reminder, Robert.

Language evolution is directed by many factors, some internal to the language, some external (social, ...).
We don't know all the factors, and we don't fully understand how those we're aware of interact.
As a consequence, we can only partly explain the evolution of a language, and even less predict its future evolution.