Irish grammar spotlight - sĂ©imhiĂș or lenition
The sĂ©imhiĂș (shay-voo) is the process of adding an 'h' between the first and second letter of a word, for example, the word mĂĄla (maw-la) (bag) would become mhĂĄla (vaw-la).
The sĂ©imhiĂș softens the start of the word, as above it turns m into a v sound.
Only some letters take a sĂ©imhiĂș, a, e, i, o, u, h, j, l, n, r, v, and s (though s has some exceptions) are all exempt from sĂ©imhiu.
This means the letters b, c, d, f, g, m, p, t, and occasionally, s.
The sĂ©imhiĂș aspirates the consonant, which means that while saying the consonant you exhale a puff of air, similar to how the 'h' is pronounced in english words like house, essentially you combine the consonant with 'h' sounds.
Approximately, the consonants go from:
buh > vuh, kuh > khuh, duh > yuh, fuh > wuh, guh > ghuh , muh > wuh/vuh, puh > fuh, tuh > huh, suh > huh. (Note pronunciations may vary between dialects.)
So when do you use a sĂ©imhiĂș?
Well, a sĂ©imhiĂș is always used after the first and second person possessive pronouns, as well as the masculine third person (note this is the way irish diffrentiates 'a' into his or her so the sĂ©imhiĂș here is quite important) This makes mĂĄla go to mo/do/a mhĂĄla (my/your/his bag)
A sĂ©imhiĂș is used after the 'vocative a', the vocative a is essentially a call to get someones attention, for instance, the sentence 'Hey SĂ©an!' would turn to 'A ShĂ©ain' (note, in the vocative you also put an i before the last letter)
When conjugating the past and conditional tenses you add a sĂ©imhiĂș (with some exceptions)
When using 'an' (meaning the) before a feminine noun you add a sĂ©imhiĂș to the noun such as fuinneog to an fhuinneog
When listing a number of items 1 through 6, i.e. one boat is aon bhåid, six boats are sé bhåid.
After certain prepositions, such as ar (on/in/at/for), do (to/for), de(of/like), sa, faoi (under), Ăł (from), and roimh (before), as well as preverb modifiers like ba and mĂĄ (if)
Most negatives (words after nĂ, nĂor, nĂĄr) take a sĂ©imhiĂș
Proper nouns are lenited when indicating ownership, e.g gĂșna Chaoimhe (Caoimhe's dress)
When compounding words, all words except from the first are lenited. (e.g. bangharda)
There are other cases but these should cover just about every case. This amy seem like a lot but it really isn't a massive deal, play it by ear. Worst comes to worst, feel it out! If it feels like it should take a sĂ©imhiĂș, throw one in, no ones going to kill you for it.
(here and here are some other good explanations for when to use a sĂ©imhiĂș)