Nouns ending in -acy and -asy
The ending -acy is much more common than -asy. Here are some of the most familiar nouns ending in -acy:
accuracy; conspiracy; intimacy; piracy; legacy; intricacy; primacy; adequacy; delicacy; legitimacy; aristocracy; pharmacy; privacy; democracy; lunacy; bureaucracy; literacy; supremacy; fallacy; numeracy; obstinacy; immediacy.
There are only four nouns in standard English that end in -asy. It's best just to remember these:
apostasy; ecstasy; fantasy; idiosyncrasy.