idiosyncrasies

noun, plural id·i·o·syn·cra·sies.

1. a characteristic, habit, mannerism, or the like, that is peculiar to an individual.
2. the physical constitution peculiar to an individual.
3. a peculiarity of the physical or the mental constitution, especially susceptibility toward drugs, food, etc.Compare allergy(def 1).

noun plural -sies

1. a tendency, type of behaviour, mannerism, etc, of a specific person; quirk
2. the composite physical or psychological make-up of a specific person
3. an abnormal reaction of an individual to specific foods, drugs, or other agents

n.

c.1600, from French idiosyncrasie, from Greek idiosynkrasia “a peculiar temperament,” from idios “one’s own” (see idiom) + synkrasis “temperament, mixture of personal characteristics,” from syn “together” (see syn-) + krasis “mixture” (see rare (adj.2)). Originally in English a medical term meaning “physical constitution of an individual.” Mental sense first attested 1660s.

n.

1. A structural or behavioral trait peculiar to an individual or a group.
2. A physiological or temperamental peculiarity.
3. An unusual individual reaction to food or a drug.