[From Manx Soc vol 2, Kelly's Manx Grammar]
Manks nouns have ordinarily but two Numbers, the Singular and the Plural.
We seem also to use the dual, when daa, two, or both, may be compounded with a substantive; as, daa ghooinney, two men; daa chass, two feet; daa hie, two houses; daa ven, two women, literally, two woman, &c.
Substantives compounded, or put in apposition with numerals, in the first and second number of every score, instead of the plural, use the singular number; as, un hooill, one eye; daa hooill, two eyes; three sooillyn, three eyes; feed sooill, twenty eyes; un hooill as feed, one-and-twenty eyes; da-eed sooill, forty eyes; three-feed sooill, sixty eyes, &c.* The word laa, a day, when put after a numeral, may be used throughout in the singular number: thus--un laa, daa laa, three, kiare, queig, &c., laa.
Some substantives want the singular number: as, cloan, children; maase, cattle; sleih, people, &c. Others want the plural: as, arran, bread; jough, drink; sollan, salt; eeym, butter; feill, flesh; fuill, blood; bainney, milk; niart, strength; fort, ability; keayney, weeping; trimshey, sorrow; and the like.
And the names of metals: as, airh, gold; argid, silver; prash, brass; yiarn, iron; stainney, tin, &c.; and all proper names.
* The Manks count by scores. The score, yn feed has no plural termination. Every noun numbered by the score is in the singular form; as--a score man, two score man, three score man.--Ed.