Peculiarity (noun)

1. A distinctive feature or attribute that characterizes or defines a person or thing.
2. A characteristic that is peculiar to a particular person or thing.

Origin:

Early 16th century (as a noun in the sense 'strangeness'): from latin peculiaritas, from peculiaris "belonging to a particular person", from peculium "private property".

Examples:

1. The peculiarities of his writing style are what make his work so unique.
2. One of the peculiarities of this town is the way they celebrate holidays.
3. The peculiarities of this antique clock are what make it so valuable.
4. Her peculiarities were what made her so endearing to her friends and family.
5. The peculiarities of this ecosystem make it particularly susceptible to climate change.