I am making my way through Essential Irish Grammar by Éamonn Ó Dónaill, and I am very confused by something I read in it. According to this book, lenition results in the following changes: b -> bh, c -> ch, d -> dh, f -> fh, g -> gh, and s -> sh. That seems reasonable, but then the book also says that m and p become bh. Are those just (really unfortunate) typos? Shouldn't those become mh and ph, respectively?

definitely a typo. Mh and ph indeed.
I'm afraid hundreds of other learners will get lost because of that typo, if they can't ask someone...

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Thank you so much! The original copyright on the book is 2005, so I shudder to think of how many people might have gotten confused...very bad errors indeed, and right there on page 2!

Hi, welcome to the forum.

However, I would say "s" is lenited by a t-prefix "ts" more often than with a "h". That's why you find:

an tseachtain not an sheachtain

as "seachtain" the "week" is a feminine noun.

But,

an sagart "the priest". No lenition as "sagart" is masculine.

Also,

The Caighdeán lenites "s" when preceded by the preposition+article "sa": sa tsráid not sa shráid.

However Munster Irish lenites "s" whether it be feminine or masculine when preceded by "sa/ insa":

insa tsiopa, insa tseomra for example.

and also in Munster, "s" is lenited with "t" after don/den ("do" +article "an"= don) don tseachtain etc...

However, other prepositions tend to lenite "s" with "h" when appropriate.

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Thank you so much for elaborating! The book did go on to give some other useful (and I think accurate) guidelines on lenition, and those led me in the right direction--until I got to an exercise in which I was asked to come up with the form of meánscoil that would follow the definite article, at which point I dutifully lenited in accordance with the typographically compromised advice I had been given. The result, which caused me pain and violated all my language instincts, was:

an bheánscoil

...which form did not match up with the answer in the answer key, which is why I started looking at whether there was something wrong in the explanatory text.

Ah, the adventure of language learning!

, the joy of language learning indeed!

I'll run through some of the rules, when nouns are preceded by the definite article: The changes brought about are called initial mutations and you are about to see one of these changes in the form of a "séimhiú or lenition "h" or "t-prefix"

The Irish alphabet: a, b, c, d, e, f, g, h (special letter of the alphabet), i, j (recent loanword: jíp), l, m, n, o, p, r, s, t, u, z (recent loanwords: zú)

Irish only has the definite article:

a man: fear
a woman: bean

A man is over there: Tá fear thall ansin

the man: an fear
the woman: an bhean

The man/woman is over there: Tá an fear thall ansin/ Tá an bhean thall ansin

Feminine consonants when preceded by the definite article:

b/c/f/g/m

An bhean (the woman)
An chistin (the kitchen)
An fharraige (the sea)
An Ghaeilge (the Irish langauge)
An mheánscoil (the secondary school)
An pháirc (the park)

exception: feminine consonants beginning with "t" and "d" are never lenited when preceded by the definite article. Though they may be lenited in other circumstances i.e when preceded by prepositions, which you'll see soon enough.

An tine (the fire)

But the house is on fire:

Tá an teach/tigh trí/tré thine.
Where trí/tré are prepositions.

An duilleog

j, l,n or r [b]are never lenited in Irish[/b] an naomhóg etc...

Feminine consonants that begin with "s" when preceded by the definite article are given a t-prefix:

an tseachtain (the week)
an tsochraid (the funeral)

etc...

Feminine vowels when preceded by the definite article:

No changes occur:

An abairt
An eaglais
An iníon
An oifig
An uair

Masculine nouns beginning with consonants preceded by the definite article:

No lenition occurs regardless i.e

No lenition occurs on "t" or "d"

An bád (the boat)
An cat (the cat)
An doras (the door)
An fear (the man)
An gairdín/ an garraí (the garden)
an mála (the bag)
an póca (the pocket)
An tórramh (the wake)

No t-prefix on masculine consonants beginning with "s":

An sagart (the priest)
An scamall (the cloud)

No lenition on j,l,n,r anyway

Masculine nouns beginning with vowels preceded by the definite article:

These nouns are given a t-prefix:

An t-athair (the father)
An t-éan (the bird)
An t-iasc (the fish)
An t-ospidéal (the hospital)
an t-úll (the apple)

However, if the noun has to be capitalised i.e the Father (i.e GOD) then: An tAthair not An t-Athair nor an T-athair.

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Wow, this is fantastic! Thank you so much. Really, really helpful, and I am grateful.

As your post notification came in, I was doing the third lesson from Buntús Cainte Beginners MP3 Course from Talk Irish.

I had decided that if I read too many more Irish words without getting a better sense of the relationship between written letters and actual pronunciation, terrible things might happen! I'm so far finding the lessons quite helpful.

no bother at all, keep up the good work!

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A prefixed "t-" isn't technically lenition, as far as I know.

Redwolf

You are right, a prefixed t is... a prefixed t
Lenition means the initial consonant of a word is "softened" (most of the time, in Irish grammar, it means that a stop becomes a fricative).
You prefix t to an initial s after the article in the same cases you would lenite another consonant (namely feminine singular nominative and masculine singular genitive).

But in other cases (ie. not after articles) you really lenite an initial s as well as any other consonant (ex: mo shaol, mo charr, mo ghaosán...).

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