The Genitive Case (An Tuiseal Ginideach)

Usage
1.

With two nouns together, e.g. ainm fir, "a man's name".

2.

After the ag [verbal noun] construct. Actually the same as above: The verbal noun is a noun.

Tá mé ag ithe feola. I am eating meat g. of feoil
ag caitheamh amsire spending time g.of aimsire
ag imirt peile playing football g of peil
3.

After
roinnt "some"
neart "plenty"
mórán "many"

E.g. roinnt aimsire "some time"

4.
Prepositional Phrases that are followed by the genitive
ar feadh throughout (a time period)
ar fud throughout place
ar son for, on behalf of
tar éis after
i lar in the center
i rith during time
deireadh end
Examples
i rith an lae during the day
deireadh seachtaine weekend

First Declension - firinscneach

Examples
fear ainm fir ainm an fhir
bord méid boird méid an bhoird
oileán "ïsland" ainm oileáin
ospidéal ospidéail
corp coirp
samradh "summer" samraidh

Second Declension - baninscneach

Examples
bialann méid bialainne méid na bialainne
uair i rith uaire i rith na huaire
seachtain i rith seachtaine i rith na seachtaine (the noun is not prefixed with a t-)
fuinneog méid fuinneoige méid na fuinneoige
sraid méid sraide méid na sraide
cill "church", "churchyard" cille
maidin maidine

Third Declension I - firinscneach

Examples
rud méid ruda méid an ruda
muinteoir ainm muinteora ainm an mhuinteora
ceacht "lesson" i rith ceachta i rith an cheachta
fuacht "cold, chill" i rith fuachta i rith an fhuachta
am "time"

Third Declension II - baninscneach

Examples
eacnamaíocht "economy, economics"
filíocht "poetry"
litríocht "literature"
bliain i rith bliana i rith na bliana

Fourth Declension

Examples
siopa m méid siopa méid an tsiopa
cailín m ainm cailín ainm an chailín
bia m méid bia méid an bhia
oíche f i rith oíche i rith na hoíche
uisce m méid uisce méid an uisce
poitín m méid poitín

Fifth Declension and Irregulars

Not a lot of patterns here. Some -ir, -air words

Examples
beoir f méid beorach méid na beorach
litir "letter" f méid litreacht
cathaoir f cathrach
athair m ainm athar ainm an athar
cathair "city" f ainm cathrach ainm na cathrach
máthair f ainm máthar ainm na máthar
leaba f méid leapa méid na leapa
cara m ainm carad ainm an charad
deoch "drink" f méid dí méid na dí (d is a dental, so no lenition)
mí "month" f i rith míosa i rith na míosa
bean f ainm mná ainm na mná
lá m i rith lae i rith an lae
teach m méid tí méid an tí (t is a dental, so no lenition)