- rarity, rareness, infrequency - noteworthy scarcity
--1 is a kind of scarcity, scarceness
- rarity, tenuity, low density - a rarified quality; "the tenuity of the upper atmosphere"
--2 is a kind of density, denseness
- curio, curiosity, oddity, oddment, peculiarity, rarity - something unusual
--3 is a kind of object, physical object
--3 has particulars:bric-a-brac, knickknack, nicknack, knickknackery, whatnot; collectible, collectable; collector's item, showpiece, piece de resistance