Irish spelling might at first seem quite difficult and strange. It certainly has its peculiarities but with a bit of studying, you will begin to see the method in the madness and you will be reading like a pro.
A central concept in Celtic languages are consonant mutations. In the Goidelic languages which include Irish, Scots Gaelic and Manx, consonants are grouped into two groups called broad and slender.
A simplifed way of looking at this is that broad consonants are pronounced at the back of the mouth and slender consonants are pronounced at the front of the mouth.
Irish uses 5 vowels in its writing system: a, e, i, o and u.
Pronounce the following English words: father, fore and tune. These contains the vowel "a", "o" and "u". In linguistics, the sounds "a" in father, "o" in fore and "u" in tune are called back vowels because they are pronounced at the back of the mouth.
These vowels affect the consonants around them to a greater and lesser degree in all languages. Compare the pronunciation of "l" in "feel" vs "pool". You pronounce the "l" further back and down in the mouth with the word "pool" because the "oo" sound is pronounced further back in the mouth than the "ee" sound. When people speak fast the tongue moves in a way that make things easier to say.
Take the "l" in "feel" and try to pronounce "pool" with that kind of "l". It will sound quite weird. Try pronounce "feel" with a "l" from "pool". They sound weird because you are not pronouncing the "l" in the same way you usually do. Its still understandable but it's weird.
Remember this "feel" "l" and "pool" "l". Irish takes this difference in the consonants and dials it up to 11.
Once, long ago, Irish was much simpler. An "l" was an "l". But even then there were slight differences in how the consonants were pronounced depending on what vowels were around them. Over time the differences got larger, and eventually the differences between these two types of consonant pronunciations became part of the grammar and started being perceived as different consonants altogether.
The vowels "a", "o" and "u" caused the consonants to be pronounced further back in the mouth. The consonants pronounced further back in the mouth are called broad consonants and the consonants pronounced further forward in the mouth are called slender consonants.
Consonants change from broad to slender or vice versa to mark grammatical roles amongst other reasons such as marking grammatical gender.
The reason why Irish spelling looks weird at first is that it makes slender and broad consonants explicit. Instead of using a different character for broad and slender, Irish uses vowels (and sometimes extra consonants) to indicate if a consonant is slender or broad.
Ok, so how do you know which vowel to use? Actually, we use the ones we have already been talking about. "a", "o", "u" indicate a broad consonant (pronounced in the back of the mouth) and "e" and "i" indicate a slender consonant (which are pronounced at the front of the mouth).
The way this is taught is that slender goes with slender and broad goes with broad. This means that the vowel next to a consonant determines whether it is slender or broad. Let's look at an example
"bac" means a barrier or constraint. "a" makes the consonant broad, so "b" and "c" are pronounced broad.
How do we pronounce broad consonants?
Think back to the word "feel". In the International Phonetic Alphabet the pronunciation of "feel" is written as /fiːlˠ/. The "l" used in "feel" can also be written as /ɫ/. When you pronounce the "l" in "feel" you are actually pulling your tongue backwards until the back of it pushes against the soft palate at the back of your mouth.
In linguistics when you pronounce a consonant with your tongue pulled back against the soft palatte, it is said to be velarised. A small "ˠ" is added to the IPA pronunciation to indicate velarisation.
Let's look at "bac" in Irish. The "a" vowel makes the consonants broad, in other words, they are both velarised. In IPA the pronunciation of "bac" is written as /bˠak/. The "k" doesn't have a "ˠ" after it because a "k" sound is already a velar sound (velar means it is pronounced with the tongue pushing against the soft palatte at the back of the mouth).
Let's look at another example.
"bog" means "soft". "o" is a vowel that makes the consonants broad. So the "b" in "bac" and "bog" are pronounced the same. In IPA this would be /bˠɔg/. "k" and "g" are velar consonants so they don't get the small velarisation symbol.
"lus" means "plant" or "herb". "u" is a back vowel like "a" and "o", so it makes all the consonants broad. In IPA the pronunciation of "lus" is written as /lˠʊsˠ/.
So far we have looked at broad pronunciation. Let's look at slender pronunciation. The slender version of consonants are pronounced by pushing the tip of the tongue against the front hard palatte. In linguistics this is called palatilisation and the IPA uses a small "j" to indicate this. Some consonants in English became palatilised over time. The word "ship" is one example. Compare the sound "s" to the sound "sh". They are both single sounds but one is palatilised and the other isn't. The "sh" sound is written as /ʃ/ in IPA.
"dise" is a grammatical form of the word "for". "i" makes the consonants slender so it is pronounced /dʲɪʃə/. To pronounce /dʲ/ just pronounce a "d" and a "y" together (like in English "you" or "yet"). Basically just put your tongue against the front hard palatte while pronouncing a consonant.
"nid" is a grammatical form of the word "nead". Like "dise", the "i" makes the consonants slender so its pronounced /nʲɪdʲ/.
So far we have only been talking about words with one vowel in them. A vowel makes both consonants the same type, either both slender or both broad. How would you spell something that has one broad and one slender?
This is where Irish spelling gets a bit more complicated but not much. Remember, "a", "o" and "u" are broad, and "e" and "i" are slender. All you have to do is put in another vowel of the other type to "block" it from having the same type as the first consonant. You can work out which type a consonant is just by looking at the vowel next to it. Once you understand the concept of broad and slender, it actually becomes much easier to get your head around what the letters in each word are doing.
Lets look at the word "bail" which means "prosperity" or "validity". "b" is next to "a" which is a broad vowel so b is pronounced as /bˠ/ and l is next to a slender vowel so it is pronounced as /lʲ/. There is a bit of a complication with "ai". How is this pronounced? Irish tends to follow certain patterns. If you want an "a" sound with broad on the left and slender on the right, then you use "ai".
There are a lot of different combinations of broad and slender vowels but not every combination is used. Mathematically there should be about 20 different combinations but around 10 are used.
Unfortunately when it comes to the vowel combinations you pretty much need to learn what sound they make because Irish has been written for a long time and some of the sounds in words has changed but the spelling kept the same. But once you know the pronunciation of a given two letter combination of vowels it will have that pronunciation most of the time. All languages have exceptions though, but Irish spelling is way more consistent than English.
For instance "ao" is pronounced like English "ee" which in IPA is /i/ and "oi" is pronounced like English "ai" in "fair" or "air" which in IPA is /ɛ/.
Here are the main vowel combinations with pronunciation between slashes (which is the usual way to indicate IPA pronunciation)
"ai" and "ea" are pronounced /a/
"ei" and "oi" are pronounced /ɛ/
"io" and "ui" are pronounced /ɪ/ (/ɪ/ is the short "i" in English "bit")
"ao" are pronounced /i/
"ia" is pronounced /iə/
"iu" is pronounced /u/
"eo" is pronounced /o/
"ua" is pronounced /uə/
Fada
The accute accent, or fada, indicates a long vowel. In combinations of two or three vowels and one of the vowels has a fada, its usually the one that is pronounced. A classic example of a word with a fada is the name Seán. You have probably seen this name before. The reason its written like that and pronounced like that is because its actually an Irish name. The "se" is pronounced as /ʃ/ since "e" indicates a slender consonant. The fada indicates a long vowel so "á" is pronounced /ɑː/ and the "n" is next to an "a" so it is velarised as /nˠ/. It is pronounced /ʃɑːnˠ/.
The fada is important because without it the word becomes "sean" pronounced as /ʃanˠ/. The vowel changes and is not long anymore. "Seán" is an interesting name because it is the Irish version of the name "John". Back in the day names were often changed to fit the sound system of the language of an area.
Here are the broad slender pairs in IPA. If you want a detailed explanation on how to pronounce these, play the sound clip or read the explanation at the IPA article on Wikipedia https://en.wikipedia.org/wiki/International_Phonetic_Alphabet. They go into a lot of detail and you can read up on any of the character you need help with.
Broad b /bˠ/, Slender b /bʲ/
Broad c /k/, Slender c /c/
Broad d /dˠ/, Slender d /dʲ/
Broad f /fˠ/, Slender f /fʲ/
Broad g /g/, Slender g /ɟ/
Broad m /mˠ/, Slender m /mʲ/
Broad n /nˠ/, Slender n /nʲ/
Broad p /pˠ/, Slender p /pʲ/
Broad r /ɾˠ/, Slender r /ɾʲ/
Broad s /sˠ/, Slender s /ʃ/
Broad t /tˠ/, Slender t /tʲ/
There are two other big parts of Irish spelling which are lenition and eclipsis. If you have been wondering why the name Niamh is pronounced "neev" well, you have come to the right place. Lenition is a word from Latin which means "softening".
The effects lenition and eclipsis (which are two of the consonants mutations in the grammar) have on spelling is actually quite simple. Lenition is shown by an added "h". Eclipsis just adds the new sound to the front of the word. So those two systems interact with the spelling in very simple ways. The difficult part is knowing when to apply lenition or eclipsis.
What does lenition sound like?
Let's start with the sound "p". It's a little puff of air from between pressed lips. Now open your lips slightly and blow a constant stream of air. You are now making the IPA /ɸ/ sound. Actually, this is the sound that is written as "f" when Japanese words are written with the Latin script. Mt. Fuji is actually pronounced /ɸɯʑi/. Now bring your bottom teeth up until they touch your teeth and blow a stream of air. You are now pronouncing "f".
We have now gone all the way from "p" to /ɸ/ to "f". This is lenition in action. /ɸ/ and "f" are a bit like lazy "p"s. The lips aren't as tight or controlled. Languages are always changing and sometimes sounds get softer or "more lazy". Lenition is one of the ways sounds can change over time.
Have you ever wondered why "phone" is written with a "ph"? Well, it's exactly this phenomenon. A "p" sound (it was actually an aspirated p, that's why it was spelled "ph") softened over time to become an "f" sound but the spelling was kept the same. And lenition happened in the development of English too.
The granddaddy of all the Germanic languages called Proto-Germanic developed out of an even older language called Proto-Indo-European. Latin is one of the many descendants of Proto-Indo-European. In Latin, "father" is "pater". The PIE word for "father" had a "p" sound in the beginning and that "p" sound was kept as it developed into Latin. But as PIE changed over time into Proto-Germanic, the "p" sound got softer eventually becoming an "f". This explains the connection between "fish" and Latin "piscis", English "foot" and Latin "pes".
When a sound like "p" becomes a breathy continuous "f" it is said that it become a fricative. English has a lot of fricative sounds like "f", "v", "th", "s" and "z". "p" became "f", "t" became "th" (compare "thou" with "tu" and the "th" in "father" vs "pater"), and "k" became IPA /x/. The /x/ sound eventually got softened further to /h/ which explains the connection between English "house" and Spanish "casa" which retained the PIE /k/ sound.
So lenition is not uncommon. What's uncommon is that the lenition would become a part of grammar. In English and other languages lenition acts on a consonant to change it and the change sticks whereas in the Celtic languages lenition only happens in certain places dictated by grammar.
Because its useful to understand the connection between lenited sounds and their unlenited versions, people writing Irish decided to keep the original letter and just add an "h". This is why Irish looks so strange at first. The original sound is written instead of the sound actually being produced. It would be like if we wrote "phater" in English and you had to know how "h" changes the sounds of words.
You already used to "ph" for "f". Irish uses other combinations that you will be used to but they are pronounced differently. "ch" is pronounced /x/, like in German "Macht", "sh" is pronounced /h/ and "th" is pronounced /h/.
The ones you will not be used to are "bh", "dh" and "mh".
You can do a similar exercise with "b" that we did with "p". Put your lips together for "b" and then open them slightly and produce a stream of air. You have just made the IPA /β/ sound. If you now put your teeth against your lips and make a stream of air you are now making a "v" sound. So "b" to /β/ to "v". Over time "b" and "v" merged in Spanish into a /β/ and then to a /b/ although /β/ is still used in certain phonetic environments.
The lenition of "b" into "v" happened in the Germanic languages too, but not in German, so German is actually less divergent than you might think. German "leben" is cognate with English "live" and Dutch "leven" but it is also cognate with Russian "лепи́ть (lepit')". "p" and "b" are much closer, differing only by voicing.
"dh" got lenited to /ɣ/ which is a sound English used to have but not anymore. If you can pronounce /x/ then you can just voice it to become /ɣ/. This sound is written as "gh" in English but eventually became silent. In some words like "cough" or "laugh" it became an "f". Compare "laugh" with German "lachen". "mh" is the same as "bh" so it becomes /v/. The "gh" in Irish is also /ɣ/ just like "gh" used to be pronounced in English.
Eclipsis
Eclipsis is a "darkening" of a consonant in certain situations. When a consonant is eclipsed the new consonant replaces the original when the word is pronounced (but in writing the original consonant is retained and the new consonant is added to the front). It is called eclipsis because the new consonant covers or eclipses (like a solar eclipse) the original consonant.
In eclipsis, a voiceless stop such as p, t, k is voiced and voiced stops such as b, d, g become nasal.
For example, "teanga" (meaning language) is pronounced /tʲaŋɡə/. The "e" next to the "t" makes the "t" palatal. When eclipsis is triggered, "teanga" becomes "dteanga" /dʲaŋɡə/. Here the /tʲ/ becomes /dʲ/ but in writing the original word is kept and the new letter is added to the front.
Here is the full list
If a consonant was velarised, it stays velarised. Some with palatislisation
When p becomes eclipsed
/pˠ/ becomes /bˠ/
/pʲ/ becomes /bʲ/
When t becomes eclipsed
/tˠ/ becomes /dˠ/
/tʲ/ becomes /dʲ/
When c becomes eclipsed
/k/ becomes /ɡ/
/c/ becomes /ɟ/
When f becomes eclipsed
/fˠ/ becomes /w/
/fʲ/ becomes /vʲ/
p, t, k and f are stops because they are produced by a short puff of air and then the puff of air is stopped.
If the stop is a voiced stop then it becomes nasal when it gets eclipsed
The word "bainne" /bˠaːnʲə/ (meaning milk) becomes "mbainne" /mˠaːnʲə/
Here is the full list
If a consonant was velarised, it stays velarised. Some with palatislisation
When b gets eclipsed
/bˠ/ becomes /mˠ/
/bʲ/ becomes /mʲ/
When d gets eclipsed
/dˠ/ becomes /nˠ/
/dʲ/ becomes /nʲ/
When g gets eclipsed
/ɡ/ becomes /ŋ/
/ɟ/ becomes /ɲ/
If you want a detailed explanation on how to pronounce these, play the sound clip or read the explanation at the IPA article on Wikipedia https://en.wikipedia.org/wiki/International_Phonetic_Alphabet. They go into a lot of detail and you can read up on any of the character you need help with.