Nadir

Illustration of the relative position of cenit and nadir. (Note.- The terms appear in English.)

In astronomy, the nadir (from Arabic نظير nathir, "opposite") is the intersection between the vertical of the observer and the celestial sphere.. That is, if you imagine a line that passes through the center of the Earth and our location on its surface, the nadir is on that line, below our feet. In the opposite direction, is the zenith.^{[citation required]}

In medicine, the lowest point of fluctuations of a symptom or a clinical interval is called nadir. Its use in fever describes the lowest temperature in a period of time; in neurology it denotes when a symptom or a set of symptoms begin to disappear, in obstetrics its use refers to the strength of uterine contractions or hormone levels, and in oncology it refers to the lowest hematological count (leukocytes, erythrocytes and platelets). of a given patient in a given period after a treatment.