A hiccup (/ˈhɪkəpˌˈhɪkʌp/ HIK-əp, HIK-up; also spelled hiccough) is an involuntary contraction (myoclonic jerk) of the diaphragm that may repeat several times per minute. In medicine, it is known as synchronous diaphragmatic flutter (SDF), or singultus, Latin for the act of catching one's breath while sobbing. The hiccup is an involuntary action involving a reflex arc. Once triggered, the reflex causes a strong contraction of the diaphragm followed about 0.25 seconds later by closure of the vocal cords, which results in the classic "hic" sound.