Hoigh, an dithis agaibh! or Personal numerals

Why does Gaelic have special numbers for counting people? It just does. Some languages do, some don't - some even have special counting words for men and women - so don't complain, there's only ten to be learnt in Gaelic. Here's the numbers first, the dreaded footnotes are at the bottom:

№	counting people (irregular nouns)	counting people (regular nouns)	plural nouns
1	aonar mór aonar mór	aonar mór aonar mór	aonar mór
2	dithis fhear móra dithis bhalach móra	dithis bhan móra dithis chloinne móire	dithis chaileagan móra

3 triùir fhear móra triùir bhan móra triùir bhalach móra triùir chaileagan móra triùir chloinne móire 4 ceathrar fhear móra ceathrar bhan móra ceathrar bhalach móra ceathrar chaileagan móra ceathrar cloinne móire 5 cóignear fhear móra cóignear bhan móra cóignear bhalach móra cóignear chaileagan móra cóignear cloinne móire 6 sianar fhear móra sianar bhan móra sianar bhalach móra sianar chaileagan móra sianar cloinne móire 7 seachdnar fhear móra seachdnar bhan móra seachdnar bhalach móra seachdnar chaileagan móra seachdnar cloinne móire 8 ochdnar fhear móra ochdnar bhan móra ochdnar bhalach móra ochdnar chaileagan móra ochdnar cloinne móire 9 naonar fhear móra naonar bhan móra naonar bhalach móra naonar chaileagan móra naonar cloinne móire 10 deichnear fhear móra deichnear bhan móra deichnear bhalach móra deichnear chaileagan móra deichnear cloinne móire

1. Because they are (grammatically speaking) nouns, the numbers for counting people are followed by the genitive plural. Just as with other nouns, the plural genitive gets lenited when indefinite. Thus we have dithis fhear or dithis ghillean (lit. two of men/boys) but na dithis fear and na dithis gillean 'the two men/boys'. If it helps, you can think of these numbers as a "twosome, threesome, foursome of children, men, girls, grannies ...", it explains the genitive anyway.
2. Again, as with many rules in any languages, you will hear people say things differently - many Gaels say cóignear nighean instead of nigheannan ...
3. So just remember to use these as nouns - things like chunnaic mi dithis or an do rinn na triùir agaibh an obair? are perfectly ok.
4. Also, you only use them up to ten, after that, you count people like things, that's why you won't see that column anymore further down.
5. Gender. Yes, gender. Seeing these are all nouns, they need a gender. They are all masculine, except for dithis and triùir, so if you follow these with an adjective, it gets lenited e.g. dithis mhóra, triùir bheaga but cóignear bochda.
6. As a result, remember to prefix t- before ochdnar, e.g. in thàinig an t-ochndnar aca fadalach 'the eight of them came late'.
7. Instead of naonar, you also hear naoinear and instead of dithis dithist.
8. Even though 2 takes the dual with the ordinal/cardinal numbers, dithis is followed by the plural. Fun, eh? Remind me to tell you about counting in the Chinese languages one day.
9. Plural nouns take the only genitive the have, so clann becomes cloinne and it lenites after dithis and triùir. We haven't been able to think of a masculine plural nouns denoting living beings - do let us know if you can think of one.

The last thing to remember is that because they are nouns, these can stand on their own, e.g. thàinig an dithis a-steach 'the two (of them) came in' or chaidh triùir a-mach 'three (of them) went out'.