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(thred) 1. A thin filamentous structure, e.g., a stringy substance present in the urine in some infectious diseases of the urinary tract. 2. Suture material. 3. To guide a catheter into a narrow organ or structure, esp. into a blood vessel.


(thrĕd′wŭ rm″) Any long, slender nematode worm. SEE: Enterobius.

three-dimensional, 3D

Pert. to three spatial planes, i.e., length, width, and depth.

three-dimensional ultrasonography, three-dimensional sonography, three-dimensional ultrasound, 3D ultrasonography, 3D sonography, 3D ultrasound

SEE: under ultrasonography.


(thrē′ō-nīn) ABBR: thr. C4H9N03 Alpha-amino-beta-hydroxybutyric acid, an essential amino acid.


(thresh′ (h)ōld″) 1. The point at which a psychological or physiological effect begins to be produced. 2. A measure of the sensitivity of an organ or function that is obtained by finding the lowest value of the appropriate stimulus that will give the response.

absolute t. The lowest amount or intensity of a stimulus that will give rise to a sensation or a response.

acoustic reflex t. The decibel level that provokes reflex contraction of the stapedius muscle. Tests that measure the triggering of the acoustic stapedius reflex are used to determine the presence of sensorineural hearing loss.

anaerobic t. The point at which increased carbon dioxide production and minute ventilation result from increased levels of lactic acid during exercise.

auditory t. The minimum audible sound perceived.

t. of consciousness In psychoanalysis, the point at which a stimulus is just barely perceived.

difference t. Just noticeable difference.

differential t. The lowest limit at which two stimuli can be differentiated from each other.

erythema t. The stage of ultraviolet skin injury in which erythema of the skin due to radiation begins.

ketone t. The level of ketone in the blood above which ketone bodies appear in the urine.

ketosis t. The lower limit at which ketone bodies, on their accumulation in the blood, are excreted by the kidney. At that point, ketone bodies are being produced faster by the liver than the body can oxidize them.

pain t. The minimum level of sensory stimulation that a person will perceive as being unpleasant, noxious, or intolerable.

pressure pain t. ABBR: PPT. The applied mass per area (kg/cm2) that will elicit a complaint of pain in subjects with painful conditions, e.g., fibromyalgia, temperomandibular joint dysfunction, or vulvodynia.

renal t. The concentration at which ...

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