Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android. Learn more here!


(thal′ē-ŭm) [Gr. thallos, a young shoot + -ium (1)] SYMB: Tl. A metallic element, atomic weight (mass) 204.37, atomic number 81, specific gravity, 11.85. Its salts may be poisonous in overdose; its radioisotope is used to assess myocardial perfusion and viability.

t. 201 A radionuclide used to diagnose ischemic heart disease. When injected at the peak of exercise during a graded exercise tolerance test, it circulates to the myocardium. Images of the heart can then be obtained to aid in the diagnosis of impaired coronary blood flow or prior myocardial infarction. SEE: exercise tolerance test; redistribution.

t. sulfate A chemical used as a rodenticide. It is also toxic to humans.

thanato-, thanat-

[Gr. thanatos, death] Prefixes meaning death.


(thăn″ăt-ŏg-nō-mŏn′ĭk) [″ + gnomonikos, knowing] Pert. to the approach of death.


(thăn″ă-tŏl′ō-jē) [Gr. thanatos, death, + logos, word, reason] The study of death.

Thayer-Martin medium

(thā′ĕr-măr′tĭn) A special medium used for growing the causative organism of gonorrhea, Neisseria gonorrhoeae.


Todd-Hewitt broth.


(thē-bā′ĭn) An alkaloid present in opiates and poppy seeds.


(thē′kă) pl. thecae [Gr. theke, sheath] A sheath or investing membrane.


(thē′kăl) [Gr. theke, sheath] Pert. to a sheath.

theco-, thec-, theci-

[Gr. thēkē, case, cover] Prefixes meaning sheath, case, receptacle.


(thē′kō-dŏnt) [theco- + odont-] Pert. to or having teeth that are set in sockets.


(thē-kō′mă) [″ + oma, tumor] A spindle-cell tumor of the ovary often occurring during or after menopause. It is usually benign but may present with elevated serum tumor markers, adhesions to neighboring structures, or ascites, all of which may initially suggest prior to its removal that the tumor is malignant.

thel-, thelo-

[Gr. thēlē, nipple] Prefixes meaning nipple.


(thē-lăr′kē) [″ + arche, beginning] The beginning of breast development, a milestone that typically occurs by about age 13 in the U.S. SEE: pubarche; semenarche.


(thē′lē-ŭm) pl. thelia [L.] 1. A papilla. 2. A nipple. 3. A cellular layer.

thematic apperception test

A projective test in which the subject is shown life situations in pictures that could be interpreted in several ways. The subject is asked to provide a story of what the picture represents. ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.