I have just started trying to learn Irish using the two Teach Yourself texts (Dillon and Ó Cróinín; and O'Sé and Sheils). I am confused on how to modify nouns following the definite article "an" when the noun begins with an s. In particular, Dillon and Ó Cróinín says that an s before l, n, or r is changed to t after the article "an" and written ts-. However, O'Sé and Sheils says that this use of ts- occurs with feminine nouns (and by implication NOT with masculine nouns) that begin with s (and by implication regardless of what letters follow) in the nominative singular case and with masculine nouns in the genitive singular case.

My guess is that this is not a big issue, but I find myself getting stuck on these little points!

Go raibh maith agat,

Dennis Leyden

When it's the little points that are the problem, you know that you're making progress. In the nominative/accusative, the rule applies only to feminine nouns (except in the case of few consonant clusters that would be difficult to pronounce, although ... well :-). In the genitive, the rule flips and is applied to masculine nouns.

* Nom./Acc.: *

Masc:

Tá an súgán casta. The rope is turned/twisted.
An bhfeiceann tú an séipéal? Do you see the chapel/church?
Tá an sneachta bán. The snow is white.

Fem:

Tá an tsúil glas. The eye is gray.
Tá an tsrón ataithe. The nose is swollen.
Cuir an tslat sa chúinne. Put the rod in the corner.
Ní réidh an tsnaidhm í le scaoileadh. It's not an easy problem to solve.

but:

Tá an stail láidir. The stallion strong. (Stail is feminine gramatically)
an scian the knife
* Genitive *

Masc:

doras an tséipéil the chapel door
cailín an tsiopa the shopgirl
casadh an tsúgáin the twisting of the rope
titim an tsneachta the snowfall
deireadh an scéil the end of the story (no 't' before 'sc')

fem:

mogall na súile the eyeball
moing na staile the stallion's mane
ceann slaite the end of the rod
ceann sceana knife-end/point
scaoileadh na snaidhme the loosening of the knot, the resolution of the problem

ceann na slaite and ceann na sceana I should have written, of course. Both are correct.

Thanks for the help and all the examples. Now back to my studies so I can write this in Irish next time!