Webster's Revised Unabridged Dictionary · 1913

Rarity

Rarity (rar"i*ty; 277) , noun

[Latin raritas: compare French rareté. See Rare.]

1.
The quality or state of being rare; rareness; thinness; as, the rarity (contrasted with the density) of gases.
2.
That which is rare; an uncommon thing; a thing valued for its scarcity.
I saw three rarities of different kinds, which pleased me more than any other shows in the place. — Addison