A Quick and Dirty Guide to Irish Prepositions

"THE USUAL RULES":
The "usual rules" of initial mutation after the combination of a simple preposition and a following definite article:

• To start with, note that a plural noun preceded by a simple preposition and a definite article follows the same rules as when it is preceded just by a definite article: i.e. a consonant does not change, but a vowel takes a h-: ar na fir, ag na mná, leis na héanacha (similarly: na fir, na mná, na héanacha)
• All the difficulties are, thus, in the singular.
• The basic rule is, that the noun is eclipsed: ar an bhfear, ag an mbean. A vowel is not affected (but the t- before a masculine noun beginning with a vowel is dropped: an t-éan, but leis an éan).
• However, initial t- and d- are not eclipsed: ag an doras, ag an tine (such forms as ag an ndoras, ag an dtine are Kerry Irish).
• As an alternative, the Ulster way of leniting the noun instead is allowed in the caighdeán: ag an fhear, ag an bhean.
• In standard Irish, the initial lenitable s- (s + vowel, sn-, sl-, sr-) behaves in the same way as if there was no preposition, i.e. if the noun is masculine, it is not affected (ar an saol), but if it is feminine, the s- turns into a t-, written ts- (ar an tsráid). However, in Ulster, no difference between genders is observed here (ar an tsaol, ar an tsráid).

AG
Followed by the "dative case" (which is today for the most part equal to the nominative case, i.e. the dictionary form). When used before an article + a noun, the usual rules of eclipsis/lenition etc. apply.

Aigesna rather than ag na in plural is typically Munster Irish.

Personal forms: agam, agat, aige, aici, againn, agaibh, acu.

Before nouns with no article: ag does not affect the first sound in any way.

Main meanings of ag:

• at (in the concrete locational sense): tá sé ina sheasamh ag an doras "he is standing at the door"
• chez, in somebody's home
• at an occasion
• in somebody's possession: tá gluaisteán agam "I have a car/an automobile"

Note: The widespread habit of using le in the sense of "in somebody's home" is an Anglicism. Due to the fact that English does not have a preposition corresponding to Irish ag, German bei, or Swedish hos, with is used in English. But in Irish, if you are "staying with" somebody, you should use ag for translating "with".

AR

Followed by the "dative case" (which is today for the most part equal to the nominative case, i.e. the dictionary form). When used before an article + a noun, the usual rules of eclipsis/lenition apply.

Personal forms: orm, ort, air, uirthi, orainn, oraibh, orthu.

Before nouns with no article: The main rule is, that it lenites. However, when it refers rather to the abstract state than to the concrete position, the lenition is omitted: ar muin chapaill (on horseback) vs. ar mhuin an chapaill áirithe seo (on the back of this particular horse). 

Note:
ar dhóigh "in a way" vs. ar dóigh "excellent" (But note also ar fheabhas "excellent", which is an exception of the exception). 

There is, of course (!), even ar ndóigh "of course". (And speaking of ar + eclipsis, remember also ar gcúl. This kind of irregular eclipsis after ar is probably due to the fact that the ar we now have is a merger of several prepositions, one of them iar "after", which used to eclipse the noun.)

ar shiúl "away, gone" vs. ar siúl "happening, going on"

ar tarraingt "in traction" (when you lie with a broken bone in a hospital)

ar fionraí "suspended"

ar cois "happening, going on"

ar obair "happening, going on, proceeding"

ar dalladh "intensely"

ar fheabhas "excellent". This is an irregularity, because in exact this kind of expressions you would expect no lenition of the f-.

Main meanings of ar:

• on, upon (in the most concrete sense): ar an urlár "on the floor"
• for a price: cheannaigh mé ar ocht bpunt é "I bought it for eight pounds"
• in a relative position: tá sé ar an bhfear is fearr "he is the best man"
• under the authority of someone: tá Nearó ina Impire ar an Róimh "Nero is the Emperor of Rome"
• affected by emotion or disease: tá tuirse orm, tá fearg orm, tá slaghdán orm, tá tinneas cinn orm
• "about" in the sense of "talking about something". This usage, however, is more connected with particular verbs and phrases than that of faoi. (Compare Irish trácht ar rud and English "to remark upon something".)
• "Down upon" referring to aggression and attack is in Irish anuas ar.

AS

Followed by the "dative case" (which is today for the most part equal to the nominative case, i.e. the dictionary form). Before an article + a noun, the usual rules apply.

Personal forms: asam, asat, as, aisti, asainn, asaibh, astu.

Before nouns with no article: they are not affected at all. In Kerry, as does lenite, but this is heavily dialectal, and speakers of other dialects might find it out and out wrong. In Cork Irish, at least in Cape Clear, the historically correct form a is used instead (as being only the third person masculine singular form) - it does not affect a consonant, but adds a h- to a vowel.
Main meanings of as:

• out of; from among; from; away from
• emanating from (smells, for instance)
• material, medium: rud a ní as uisce; labhairt as Gaeilge
• in payment for: d'íoc mé deich bpunt as na hearraí "I paid ten pounds for the goods"

CHUIG

Followed by the "dative case" (see above). Before an article + a noun, the usual rules apply.

Personal forms: chugam, chugat, chuige, chuici, chugainn, chugaibh, chucu.

Before nouns without article: they are not affected at all.

Main meanings of chuig: to, towards.

Note: ag is in dialects often used instead of chuig.

CHUN

Followed by the genitive case. The usual genitive rules apply. Note though, that when chun precedes an articleless noun which is followed by a definite genitive, that articleless noun can be declined in genitive too: leas ár dtíre "the interest/greater good of our country", chun leasa ár dtíre "to the greater good of our country".

Personal forms; the same as for chuig.

Main meanings:

• to, towards
• to a conclusion, to an effect
• for a purpose

Note the older forms chum, do-chum, which you might encounter in texts printed in Gaelic type and spelled according to the old orthography.

DE

Followed by the dative case (see above). Before an article + a noun, it lenites where applicable, and turns a lenitable s- into a t- (but written ts-). Lenites nouns without an article.

Personal forms: díom, díot, de, di, dínn, díbh, díobh. The initial d- is often lenited (dh-).

Main meanings:

• from, off: rud a bhaint de dhuine "to take a thing away from somebody", stad sé den obair "he stopped working"
• attached to, sticking to: cheangail mé an rópa den bhád "I bound, attached, the rope to the boat"; cheangail mé an dá bhád dá chéile le rópa "I tied the two boats to each other with a rope"

Note: non-natives often use le to refer to what something is attached or bound to. This is wrong. In Irish you always use de for this. Le refers to whatever you use for tying them together. Thus, you tie the boats de each other le a rope.

Another note: it is quite common as dialects go to conflate de and do into one preposition, or to use do where you'd expect de. Remember this when you read native texts with Ó Donaill's dictionary.

Desna rather than de na in plural is Munster Irish. Díofa for díobh is Ulster Irish.

DO

Initial mutations as after de.

Personal forms: dom, duit, dó, di, dúinn, daoibh, dóibh. The initial d- is often lenited (dh-).

Main meanings:

• To, i.e. when giving something to someone: tabhair dom an bréagán sin "give me that toy".
• To a place (although for this I'd mostly prefer go dtí)
• For (intended for someones use; to the benefit of; etc.)
• In certain verbal noun constructions, it refers to the agent of the verbal noun: i ndiaidh dom teacht abhaile/ar theacht abhaile dom "when I had come home"

Dosna rather than do na is Munster Irish. Dófa rather than dóibh is Ulster Irish. Dom is in Ulster pronounced as d + nasal [u] sound, which is why domh and damh rather than dom are used by Ulster writers.

FAOI

Lenites a noun that follows it directly. The usual rules apply to the combination of preposition + article.

Personal forms: fúm, fút, faoi, fúithi, fúinn, fúibh, fúthu.

Main meanings:

• Under, beneath.
• About, around; also "about" in the sense of talking about something.

An Ulster acquaintance of mine suggested that there was a division of meaning between fá "about" and faoi "under, beneath" in Ulster dialect. This is possible, but my impression is that the choice of faoi, fá, fé, fó in older texts mostly depends of the phonetic environment, i.e. the vowels of the surrounding nouns (this would account for the form fó in the expression an Tír fó Thoinn "the land beneath the wave", a mythological underwater otherworld; the expression has also, probably facetiously, been used for the Netherlands).

Fé is a common spelling variant in Munster. Fésna instead of faoi na is Munster dialect.

I

Eclipses a noun that follows it directly (i dteach). 

Becomes in before a vowel. In the standard language, the combination i + an (ins an, now commonly written sa, san) lenites; in Connemara, though, it is assimilated to the "usual rules" (sa mbád rather than sa bhád). In plural, i + na becomes ins na (now commonly written sna).

Such usages as in teach instead of i dteach are basically substandard or wrong, but they do have some traditional footing in Waterford Irish.

Sa in plural is Munster dialect.

Personal forms: ionam, ionat, ann, inti, ionainn, ionaibh, iontu.

Main meanings:

• In, inside: sa teach
• In a position: i gceannas ar na saighdiúirí
• Innate capacities: tá comhábhair an cheoltóra mhaith ann 
• Role: tá mé i mo mhúinteoir
• Accusation, guilt: tá sé á chúiseamh i ndúnmharú; fuarthas ciontach i ndúnmharú é

LE

According to the standard language, it should affix a h- to a following vowel. Combines with the article to yield leis an in singular, leis na in plural. Leis an follows the usual rules.

Personal forms: liom, leat, leis, léi, linn, libh, leo.

Léithi for léi and leofa for leo are used by Ulster writers.

Main meanings:

• with
• towards, facing
• often used with verbs of interaction, transaction: labhair sé liom "he spoke with/to me"; dhíol sé a sheancharr liom "he sold his old car to me"
• with is it refers to ownership: is liom an carr úd "that car over there is mine". Note the difference: tá carr agam "I have a car", but is liom an carr "the car belongs to me".

Ó

The usual rules apply when followed by an article. When it precedes an articleless noun, it lenites. Ósna in plural is Munster dialect: ó na is standard.

Personal forms: uaim, uait, uaidh, uaithi, uainn, uaibh, uathu.
Main meanings:

• from (from a place, from a person, from a limit, from a root cause, away from someone)
• since (a point of time)

TRÍ

Becomes tríd before an. (Oops! All these years I have happily written it as tríd even before plural na!) It tends to be permanently lenited (thrí) and you do see the form tríd even before a noun without an article (this is dialectal though).

It's the usual rules before an article. Before a noun without an article, trí lenites.

Personal forms: tríom, tríot, tríd, tríthi, trínn, tríobh, triothu.
Main meanings of trí:

• through: tríd an bhfuinneog, tríd an doras
• by doing something, by using something, by doing something in a way: rinne sé an t-aireagán trí mhiontaighde "he made the invention by minutious research"
• through the medium of: ag múineadh trí Ghaeilge

UM

This preposition is only ever used in Cork Irish (well, probably sometimes in Kerry before names of holidays) and in legalese. I confess I have no exact idea what it means, but it follows the usual rules when  it comes before an article. Before a naked noun, it lenites, with the exception of labial consonants (b, m, p). For main meanings, consult the online Ó Donaill dictionary. - OK, fine, I am pulling your leg. It usually means "about, around", and it is often used with temporal nouns: um an dtaca so (yes, it is definitely a Munster preposition, so um an eclipses the t's and the d's!), um an gCáisc, um an Nollaig. In legalese, it refers to what a law or an act is about: an tAcht um Theascadh na mBod Rófhada "the Too Long Penises Amputating Act".

It has the personal forms umam, umat, uime, uimpi, umainn, umaibh, umpu. However, one of my readers pointed out on Twitter that she had never seen these forms before. They are hardly ever used anywhere else than in the native literature of Co. Cork; a book where you could expect to see them is Dónall Bán Ó Céileachair's Scéal mo Bheatha. And of course in Peadar Ua Laoghaire's books. In fact, I reckon this otherwise very marginal and dialectal preposition became part of modern Irish legalese only because Ua Laoghaire with Séadna and his other books was so influential in the early years of the revival of Irish.

ROIMH

Lenites naked nouns, but follows the usual rules with articles. The form roimis an... rather than roimh an... is Munster Irish. Also in Munster Irish, you might see genitive forms after roimh.

Personal forms: romham, romhat, roimhe, roimpi, romhainn, romhaibh, rompu.

Main meanings:

• before (in a temporal sense): roimh an Nollaig, roimh an gCáisc
• before (in an order of preference, arrival, prestige etc.), ahead of: tháinig siad abhaile romhainn
• waiting for someone: nuair a thuirling an t-eitleán i mBaile Átha Cliath, bhí cuid mhór de lucht ár leanúna ansin romhainn

THAR

Lenites naked nouns, except in sayings of a general meaning (thar barr, thar muir, thar bord, thar claí, thar smacht, thar sáile); the usual rules apply before a definite article.

Personal forms: tharam, tharat, thairis, thairsti, tharainn, tharaibh, tharstu.

Main meanings:

• over, across, to the other side of something: chuaigh Seán thar sáile agus bhunaigh sé gnó ríomhaireachta i San Francisco
• over, above: chuaigh an t-uisce thar an gcloigeann air agus bádh é
• going or getting by or past something: chuaigh siad tharainn agus an choiscéim ghasta sin fúthu
• beyond: chuaigh na páistí thar smacht ar an múinteoir bocht
• in preference to: roghnaigh mé an ceann maith thar an drochcheann

IDIR

I have always had this idea that when it means "between", it does not lenite the following naked noun, while when it means "both (...and)", it does. However, Ó Donaill tells us that it basically lenites, with the exception of certain phrases. Whatever. It does not affect a noun preceded by article, so no "usual rules" there.

Eadar is a common variant spelling, typical of Ulster writers.

It has personal forms only in plural: eadrainn, eadraibh, eatarthu. These are only used alone. If idir is followed by two pronouns, those are kept: idir sinn agus iad, idir sibh agus sinn, and so on. 

There is one book - An Fhiannuidheacht by Cormac Ó Cadhlaigh - where you see stuff like eadrainn agus iad rather than idir sinn agus iad. The book is otherwise written in a rather commonplace Munster Irish for the most part, so I don't know whether this is an archaism or a hypercorrection.

Main meanings:

• between
• both (...and)