Habetne famulus tuus unas scopas?

[Carolus Raeticus]

Salvete!

In the key to Adler's Practical Grammar it says:

Habetne famulus tuus unas scopas?

I was quite astounded when I saw the unas. "One" with a plural form? Of course, scopae is a plural form with a singular meaning, but still. Is that really correct?

Valete

Carolus Raeticus

[Alatius]

Yep, it is correct: when you want to count a single instance of a plurale tantum noun, you use "uni, unae, una", in the plural. Cicero for example repeatedly writes about "unae litterae", and so on. But if you have more than one letter, it seems that the usual thing to do is to use the distributive numerals instead: binae litterae, trinae litterae etc.

[Carolus Raeticus]

Thank you, Alatius, for the explanation.

Carolus Raeticus