What does the term 'idiosyncrasy' refer to?

The term "idiosyncrasy" refers specifically to a peculiar or distinctive behavior, characteristic, or habit that is unique to an individual or a particular group. This is often something that may seem unusual or eccentric, setting that person or group apart from others.

In this context, it highlights the notion that idiosyncrasies are idiosyncratic—meaning they stand out due to their uniqueness, rather than being common traits or widely accepted norms. The other choices represent more generalized or collective characteristics that do not capture the essence of what an idiosyncrasy is, which is fundamentally tied to individual peculiarity.