• A distinctive or unusual feature of a person or thing.

  • (Medical) An atypical physical, mental, or emotional response to stimuli


We all do strange things sometimes, often without even knowing it! You might twirl your hair when you’re on the phone, or always put your left sock on before your right with not so much as a second (or first!) thought when you’re getting ready in the morning. Sure, your idiosyncrasies may not be noticeable to you, but, to others, they might seem a little funny or odd. Your friends likely know who’s at the door when they hear your rhythmic knocks, but that’s just because yours is different from everyone else’s! That’s why it’s an idiosyncrasy.

An idiosyncrasy refers to a distinctive trait or tendency that seems unusual to someone else. When you see someone or something that has a distinguishing feature or behavior that doesn’t reflect the norm, chances are you’ve encountered an idiosyncrasy. The neighbors might think your mailman is eccentric for honking his horn whenever he turns on your road, but you know it’s just the way he does things. Even physical characteristics, like your friend’s untamable cowlick, can be considered an idiosyncrasy. In fact, anything that sets us apart from something else is technically an idiosyncrasy! From your girlfriend’s long pigtails or the bus driver’s high-pitched “Good morning!” these differences come in all shapes and sizes, and everyone finds them more or less endearing depending on their tastes.

In general, these so-called quirks are very small and inconspicuous, but they can sometimes become a defining attribute. If you find yourself dealing with a vending machine that always needs a little encouragement (i.e. kicking) before dispensing your snack, you might have reason to complain about its irritating idiosyncrasy. Before you start pointing the finger at others’ idiosyncrasies though, realize that we’ve all got more than enough quirks to go around - and some may not find them very pleasant (like your habitual recycling of dirty socks). These oddities can be found everywhere you look by dint of diversity! Even if you can’t understand why people do the things they do, you can do them a favor by accepting their idiosyncrasies for what they are.

Before the word was used to describe peculiarities more broadly, idiosyncrasy was used in the field of medicine to denote a strange or adverse reaction to a particular substance. Before doctors knew about such things as allergies, a boy who found that his eyes watered in the presence of a cat would have been told he had an idiosyncrasy. Although these “quirks” were often physical anomalies at the time, they could also just be an individual’s unique emotional response to different stimuli. Even today, psychologists might describe a person’s reaction to something as idiosyncratic if he or she responds one way, while most other people respond another way. For example, that new car smell in your Jeep might cause you to remember spending time with your dad in his auto shop when you were a kid - an idiosyncrasy for you, but for your friends that same smell may be nothing more than a clean scent. Whatever your reaction happens to be, as long as it’s unique, it could be labeled an idiosyncrasy.

Example: One of mother’s idiosyncrasies was always having to keep the utensils in the dishwasher organized.

Example: The professor swore he developed a rash when his students didn’t do their homework – an idiosyncrasy that plagued him for years.


The word idiosyncrasy comes to us from the Greek idiosynkrasia, meaning “an unusual nature or disposition” belonging to any particular person or thing. Comprised of the words idios (meaning “personal”), syn (“together”), and krasis (“combination or mixture”), this original word in a sense can be literally translated as “one’s unique blend of characteristics and temperaments.” First used in medicine in the 17th century to denote the individual elements that encompass a person’s physical and emotional makeup, idiosyncrasy slowly evolved into its modern usage, which most often includes a person’s quirks or eccentricities.

Derivative Words

Idiosyncratic: This adjective describes someone or something that has individual or eccentric traits or mannerisms. It can also be used to describe the characteristic, itself, that is peculiar to a person.

Example: The way that his shirt refused to be ironed without turning it inside out was rather idiosyncratic.

Example: Many find Iowa’s caucus methods and rules to be idiosyncratic.

In Literature

From Elizabeth von Armin’s The Solitary Summer:

"Books have their idiosyncrasies as well as people, and will not show me their full beauties unless the place and time in which they are read suits them."

Here, we see that inanimate objects can have just as much personality as people when books only reveal their treasures when they are read within certain circumstances and mindsets. This strange “behavior,” or idiosyncrasy, is the reason why every repeat read of a work of literature reveals new meanings.


  • Try wiggling your key if the lock has an idiosyncrasy.

  • Idiosyncrasies are just peculiarities!


Individual, Quirk, Psychology, Medicine

Bring out the linguist in you! What is your own interpretation of idiosyncrasy. Did you use idiosyncrasy in a game? Provide an example sentence or a literary quote.