rarity

Snow in this part of Australia is a total rarity and only happens once in a decade.

(Chinese) 澳大利亚这个地区的降雪非常罕见，十年才发生一次。

The rarity of the diamond is what makes it so incredibly expensive to purchase.

(Chinese) 这颗钻石的稀缺性正是它购买价格如此昂贵的原因。