FYI for anyone interested, the word 'músaem' also gets used to mean 'museum'.
Why is it not "Is maith liom an t-iarsmalann."? I. e. in what situations do you use the "t-" after the definite article?
The prothetic T is used after an in the following cases:
- with a non-genitive masculine noun that begins with a vowel;
- with the numeric words aon, ocht, ochtú, ochtar, aonú, ochtó, and ochtódú ;
- with a non-genitive feminine noun that begins with S followed by L, N, R, or a vowel;
- with a genitive masculine noun that begins with S followed by L, N, R, or a vowel.
In the first and second cases only, the prothetic T is followed by a hyphen if the noun or adjective begins with a lower-case letter (e.g. an t-am, an t-aonú dalta déag, but an tEarrach).
In the third and fourth cases only, the an can be part of a prepositional phrase (e.g. ar an tsráid, ag barr an tsléibhe).
It’s an iarsmalann because iarsmalann is a feminine noun that begins with a vowel.
Iarsmalann is more specific to antiquity museum. As ciat said, Músaem is ok, and most common in namung Irish museums...