Fòram na Gàidhlig

but I don't see the nominitive singular.

Hm maybe that's because the nominative singular is the citation form i.e. the entry you see IS the nominative singular...

As for Faclair I see the terms 'fir', 'gin' and 'iol' listed for each noun - what are these?

Hm have you clicked on the Help symbol? The abbreviations are explained there.

The headword is the nominative singular. The nominative case is just the regular old nothing-fancy-going-on-here case, e.g. 'balach'.

http://www.faclair.com/Help/Help.html

edit: duilich, didn't see akerbeltz's reply

Ok I understand it now, thanks. Finally

http://faclair.com/Help/Help.html#DwAbbreviations

Nominative singular is the main dictionary entry itself.

ETA: I didn't see that this thread had a second page. Consider yourself having been helped