Nonverbal communication could be gestures, idiosyncratic movements, cultural habits, posture, involuntary physiological responses to stimuli, and "costumes and scenery."

Idiosyncratic movements are those little things you do that may or may not mean much.

There may be a delay or total lack of language or the use of repetitive and idiosyncratic language.

Drug sensitivities (also called idiosyncratic reactions or unusual adverse reactions) do not involve the child's immune system or the release of histamine.

Porphyria cutanea tarda (PCT) is also called symptomatic porphyria, porphyria cutanea symptomatica, and idiosyncratic porphyria.