This grammatical feature is called An Tuiseal Gairmeach The Vocative Case. It is used when addressing someone directly by name and in the initial greeting of a letter or e-mail.

Ainmfhocail Nouns in Irish change a little in form or spelling depending on the meaning or the context in the sentence. Thankfully there are not many changes, two or three, nowadays. There used to be more but the language is being tidied up and while the older forms are still recognised and loved they are not required in ordinary day to day use by Civil Servants or school pupils.

The different forms are called Tuisil Cases. An Tuiseal Gairmeach The Vocative Case is one of these Tuisil Cases.

It is helpful to think of the A of A Áine as Dear Áine rather than Oh, Áine. A does not actually mean "dear" but is a particle indicating the Tuiseal Gairmeach or the Vocative Case (used when you are addressing or calling someone.)

Note how the initial consonant of Diarmaid is lenited / aspirated "dh" after A in the Tuiseal Gairmeach. This is an indicator of the Tuiseal Gairmeach the Vocative Case. Beware: A has many other meanings and is used in many other ways which we will meet soon.

Aspiration is also called lenition in English and in Irish séimhiú. Of the twenty six letters of the English alphabet used now in Irish only these consonants take séimhiú: b, c, d, f, g, m, p, s, t. Where séimhiú is required place a h after the consonant. The sound changes but I am not dealing with the pronunciation of Irish here at the moment.

I will deal with the Tuisil Cases later but for the moment here are some examples of the Tuiseal Gairmeach Vocative Case. All the letters that take a séimhiú lenition are included. If you learn this table you will know the letters that take the séimhiú lenition.

Note 1: The initial consonant of the name is aspirated after A if possible in the Tuiseal Gairmeach.

Note 2: The last consonant of the name is slenderised if masculine i.e. Breandán; not so if feminine! i.e. Siobhán. (Slenderise?? This is called "caolú" in Irish. Generally it means to put an "i" before the final consonant as shown above. Some words change quite considerably under the influence of "caolú" but I will leave that until later.)

Note 3: In letters Dear Sir or Madam is A chara. Duine uasal means literally "a noble person" and bean uasal a lady.

Note 4: I intended to give an indication of the changes in the sound of the lenited consonants in the last column above but in the case of those marked with an asterisk I need help from someone with a knowledge of the International Phonetic Alphabet to give me the appropriate representation of the sound in the IPA. C --> CH is easily explained by reference to the sound at the end of Scottish "loch" a lake; broad D --> DH and G -- GH are similar and are somewhat related to CH but I am sorry to admit I am out of my depth here and do not know how to describe them. For a note on broad and slender consonants click on leathan le leathan agus caol le caol.

Note 5: Regarding A Niamh and A Liam no lenition is indicated in the written form but good speakers of Irish can be heard to indicate lenition in speech. To be honest when you get into listening to native speakers of the language, and I mean those who have been reared in the unbroken tradition possessed by real native speakers of Irish, you will find that there is much to learn from the spoken word that is not written at all in An Caighdeán Oifigiúil The Official Standard.

A sad corollory of this is the singer who attempts to sing a song from the oral tradition in Irish, usually called the sean-nós, and who does not really know the sounds of spoken Irish well, will be almost unintelligible and cause excruciating embarassment to those who do know the sounds of spoken Irish.

A singer who does not appreciate the importance of the sounds of the consonants and vowels will wash out much of the attractiveness of the spoken Irish and end up with a silhouette of the language more akin to Esperanto than Irish. (Think of any foreigner you know trying to speak or sing your language!)

Unfortunately those who have published so-called "standardised" versions of the old songs in An Caighdeán Oifigiúil The Official Standard "for the schools" are no help by eliminating some of the ryhme and rhythm of the language. Leave the old songs alone. Write new ones. An Caighdeán Oifigiúil The Official Standard was never intended for literature nor for songs and poems written and published long before it came into being. They should be treated with respect and left as they have come down to us in their original form of Irish. If you want to sing a song in Irish get an early pre-1950 version of it and get someone who knows Irish well to correct your pronunciation -- again and again until you get it right. If you want to do it at all you will want to do it right.

As with any language there are good speakers with clear diction and there are mumblers but in all the dialects there are sounds which are intrinsic to good pronunciation in the language which the learner must watch out for and master. If you are only commencing on your journey into the learning of Irish don't get waylaid by the perennial argument of dialect if you can avoid it. Learn to pronounce words in the dialect of the place you are most likely to visit and write An Caighdeán Oifigiúil The Official Standard.