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Medical Dictionary


θ, upper case Θ
  • theta, eighth letter of the Greek alphabet
  • symbol for angle
τ, upper case T
  • tau, 19th letter of the Greek alphabet
  • symbol for relaxation time
  • absolute temperature (kelvin)
  • ribothymidine
  • tesla
  • tension (T+, increased tension T−, diminished tension)
  • tesla, the unit of magnetic field strength
  • tera-
  • thoracic vertebra (T1–T12)
  • threonine
  • thymine
  • tidal volume
  • tocopherol
  • torque
  • transmittance
  • tritium
  • metric ton
  • time.
  • temperature (Celsius)
  • tritium.
T and A
Tonsillectomy and adenoidectomy

T antigen
any of several proteins that are produced by some tumorigenic DNA viruses (as simian virus 40) when they infect cells and that function in the transformation of normal cells into tumor cells or into tumor-forming cells and in the unwinding and replication of the DNA of the virus

T cell
any of several lymphocytes (as a helper T cell) that differentiate in the thymus, possess highly specific cell-surface antigen receptors, and include some that control the initiation or suppression of cell-mediated and humoral immunity (as by the regulation of T and B cell maturation and proliferation) and others that lyse antigen-bearing cells. Also called T lymphocyte

T lymphocyte
T cell

T suppressor cell
Suppressor T cell

T system
the system of T tubules in striated muscle

t-butoxycarbonyl (BOC, t-BOC, Boc) (bu-toks-e-kar′bon-il)
An amino-protecting group used in peptide synthesis. SYN: tert-butyloxycarbonyl.

tert-butyloxycarbonyl (tBoc) (bu′til-oks′e-kar′bon-il)


In magnetic resonance, the time for 63% of longitudinal relaxation to occur; the value is a function of magnetic field strength and the chemical environment of the hydrogen nucleus; for protons in fat and in water, in a 1.5T magnet, about 250 msec and 3000 msec, respectively. A T.-weighted image will have a bright fat signal.

In magnetic resonance, the time for 63% of transverse relaxation to occur; the value is a function of magnetic field strength and the chemical environment of the hydrogen nucleus; for protons in fat and in water, in a 1.5T magnet, about 60 msec and 250 msec respectively. A T.-weighted image will have a bright water signal.

Abbreviation for (2,4,5-trichlorophenoxy)acetic acid.

Symbol for temperature midpoint (kelvin); melting point.

Symbol for 3,5,3′-triiodothyronine.

Symbol for thyroxine.

Abbreviation for metric ton; time.

Symbol for temperature (Celsius); tritium.

Symbol for temperature midpoint (Celsius).

Abbreviation for Terminologia Anatomica.

Symbol for tantalum.

tabanid (tab′a-nid)
Common name for flies of the family Tabanidae. [L. tabanus, gadfly]

Tabanidae (ta-ban′i-de)
A family of bloodsucking flies that includes the genera Tabanus (horsefly) and Chrysops (deerfly and mango fly), which are involved in transmission of several blood-borne parasites. [L. tabanus, gadfly]

Tabanus (ta-ba′nus)
The gadflies and horseflies; a genus of biting flies, some species of which transmit surra, infectious equine anemia, anthrax, and other diseases. [L. a gadfly]

tabardillo (tah-bar-de′yo)
Mexican term for typhus. [Sp., fr. L.L. tabardilii, pustules]

tabatière anatomique (tab-ah-te-ar′ an-ah-to-mek′)
SYN: anatomic snuffbox. [Fr. snuffbox]

tabella, pl .tabellae (ta-bel′la, -le)
A medicated tablet or lozenge. [L. dim. of tabula, tablet]

tabes (ta′bez)
Progressive wasting or emaciation. [L. a wasting away] t. infantum t. in infants with congenital syphilis. t. mesenterica tuberculosis of the mesenteric and retroperitoneal lymph nodes.

tabescence (ta-bes′ens)
The state of progressive wasting away.

tabescent (ta-bes′ent)
Characteristic of tabes. [L. tabesco, to waste away, fr. tabes, a wasting away]

tabetic (ta-bet′ik)
Relating to or suffering from tabes, especially tabes dorsalis. SYN: tabic, tabid.

tabetiform (ta-bet′i-form)
Resembling tabes, especially tabes dorsalis. [irreg. formed fr. L. tabes, a wasting, + forma, form]

tabic (tab′ik)
SYN: tabetic.

tabid (tab′id)
SYN: tabetic. [L. tabidus, wasting away]

tablature (tab-la-choor)
The state of division of the cranial bones into two plates separated by the diploë. [L. tabula, tablet]

table (ta′bl)
  • One of the two plates or laminae, separated by the diploë, into which the cranial bones are divided
  • An arrangement of data in parallel columns, showing the essential facts in a readily appreciable form
  • A platform upon which items can be placed. [L. tabula]
  • Aub-DuBois t.: t. of basal metabolic rates in calories per square meter of body surface per hour or day for different ages.
  • contingency t.: a tabular cross-classification of data such that subcategories of one characteristic are indicated in rows (horizontally) and subcategories of another are indicated in columns (vertically).
  • examining t.: a t. on which the patient lies during a medical examination.
  • external t.: of calvaria the outer compact layer of the cranial bones, aka lamina externa calvaria , lamina externa cranii, outer t. of skull.
  • Gaffky t.: a numerical rating for the classification of tuberculosis according to the number of tubercle bacilli in the sputum, ranging from 1 (one to four organisms in the whole preparation) to 9 (an average of 100 per field), aka Gaffky scale.
  • inner t. of skull: internal t. of calvaria.
  • internal t. of calvaria: the inner compact layer of the cranial bones, aka lamina interna calvariae, inner t. of skull, lamina interna cranii.
  • life t.: a representation of the probable years of survivorship of a defined population of subjects; since survivorship is changed by new methods of prevention or treatment, a diachronic study is commonly used because the main interest lies in the composite structure of the current population. (In the summarizing technique used to describe the pattern of mortality and survival in a population, survivors to age x are denoted by the symbol lx and the expectation of life at age x is denoted by the symbol x.)
  • occlusal t.: the occlusal or grinding surfaces of the bicuspid and molar teeth.
  • operating t.: a t. on which the patient lies during a surgical operation.
  • outer t. of skull: external t. of calvaria.
  • tilt t.: a t. with a top capable of being rotated on its transverse axis so that a patient lying upon it can be brought into the erect position as desired; used in experimental investigation and in physical therapy.
  • vitreous t.: the inner t. of one of the cranial bones; it is more compact and harder than the outer t., aka lamina interna ossium cranii.

    tablespoon (ta′bl-spoon)
    A large spoon, used as a measure of the dose of a medicine, equivalent to about 4 fluidrams or 12 fluidounce or 15 ml.

  • A solid dosage form containing medicinal substances with or without suitable diluents; it may vary in shape, size, and weight, and may be classed according to the method of manufacture, as compressed t., aka tabule. [Fr. tablette, L. tabula]
  • buccal t.: usually a small, flat t. intended to be inserted in the buccal pouch, where the active ingredient is absorbed directly through the oral mucosa; such a t. dissolves or erodes slowly.
  • compressed t.: a t. prepared, usually as a large-scale production, by means of great pressure; most compressed tablets consist of the active ingredient and a diluent, binder, disintegrator, and lubricant.
  • dispensing t.: a t. prepared by molding or by compression; used by the dispensing pharmacist to obtain certain potent substances in a convenient form for accurate compounding. Formerly used to prepare bulk solutions of germicidal chemicals, e.g., bichloride of mercury. Not intended for internal use.
  • enteric coated t.: an oral dosage form in which a t. is coated with a material to prevent or minimize dissolution in the stomach but allow dissolution in the small intestine. This type of formulation either protects the stomach from a potentially irritating drug ( e.g., aspirin) or protects the drug ( e.g., erythromycin) from partial degradation in the acidic environment of the stomach.
  • hypodermic t.: a compressed or molded t. that dissolves completely in water to form an injectable solution.
  • prolonged action t., repeat action t.: sustained action t..
  • sublingual t.: usually a small, flat t. intended to be inserted beneath the tongue, where the active ingredient is absorbed directly through the oral mucosa; such a t. ( e.g., nitroglyerine) dissolves very promptly.
  • sustained action t., sustained release t.: a drug product formulation that provides the required dosage initially and then maintains or repeats it at desired intervals, aka prolonged action t., repeat action t..
  • t. triturate: a small, usually cylindrical, molded or compressed disk of varying size, containing a diluent usually consisting of dextrose (glucose) or of a mixture of lactose and powdered sucrose and a moistening agent or excipient, such as dilute alcohol.

    taboo, tabu (ta-boo′)
    Restricted, prohibited, or forbidden; set apart for religious or ceremonial purposes. [Tongan, set apart]

    tabular (tab′u-lar)
    1. Tablelike. 2. Arranged in the form of a table (2). [L. tabularis, fr. tabula, table]

    tabule (tab′ul)
    SYN: tablet. [L. tabula]

    tabun (ta′bun)
    An extremely potent cholinesterase inhibitor; the lethal dose for humans is believed to be as low as 0.01 mg/kg; median lethal dosage (respiratory) is about 40 mg/min/m3 for resting persons.

    Tac (tak)
    A 55-kD polypeptide that is the one of the two chains that comprise the IL-2 receptor.

    tache (tash)
    A circumscribed discoloration of the skin or mucous membrane, such as a macule or freckle. [Fr. spot] t. blanche SYN: macula albida. t. laiteuse 1. SYN: milk spots, under spot. 2. SYN: macula albida. [Fr., milky spot]

    tachistoscope (ta-kis′to-skop)
    An instrument to determine the shortest time an object must be exposed in order to be perceived. [G. tachistos, very rapid, fr. tachys, rapid, + skopeo, to view]

    tachogram (tak′o-gram)
    Record made by a tachometer. [G. tachos, speed, + gramma, mark]

    tachograph (tak′o-graf)
    A tachometer designed to provide a continuous record of speed or rate. [G. tachos, speed, + grapho, to write]

    tachography (ta-kog′ra-fe)
    The recording of speed or rate. [G. tachos, speed, + grapho, to write]

    tachometer (ta-kom′e-ter)
    An instrument for measuring speed or rate; e.g., revolutions of a shaft, heart rate (cardiotachometer), arterial blood flow (hemotachometer), respiratory gas flow (pneumotachometer). [G. tachos, speed, + metron, measure]

    Rapid. [G. tachys, quick]

    tachyarrhythmia (tak′e-a-ridh′me-a)
    Any disturbance of the heart's rhythm, regular or irregular, resulting by convention in a rate over 100 beats/min during physical examination. [tachy- + G. a- priv. + rhythmos, rhythm]

    tachyauxesis (tak′e-awk-se′sis)
    Type of growth in which a part grows more rapidly than the whole. [tachy- + G. auxo, to increase]

    tachycardia (tak′i-kar′de-a)
  • Rapid beating of the heart, conventionally applied to rates over 90 beats/min, aka polycardia, tachyrhythmia, tachysystole. [tachy- + G. kardia, heart]
  • atrial t.: paroxysmal t. originating in an ectopic focus in the atrium. SYN: auricular t..
  • atrial chaotic t.: multifocal origin of t. within the atrium; often confused with atrial fibrillation during physical examination, aka multifocal atrial t..
  • atrioventricular junctional t.: t. originating in the AV junction, aka AV junctional t., nodal t..
  • auricular t.: atrial t..
  • AV junctional t.: atrioventricular junctional t..
  • bidirectional ventricular t.: ventricular t. in which the QRS complexes in the electrocardiogram are alternately mainly positive and mainly negative; many such cases may represent ventricular t. with alternating forms of aberrant ventricular conduction.
  • Coumel t.: a persistent junctional reciprocating t. that usually uses a slowly conducting posteroseptal pathway for the retrograde journey.
  • double t.: the simultaneous t. of two ectopic pacemakers, e.g., atrial and junctional t..
  • ectopic t.: a t. originating in a focus other than the sinus node, e.g., atrial, AV junctional, or ventricular t..
  • t. en salves: short runs of paroxysmal t. of the Gallavardin type. Cf.:Gallavardin phenomenon. [Fr. t. in salvos]
  • essential t.: obsolete term for persistent rapid action of the heart due to no discoverable organic lesion.
  • t. exophthalmica: rapid heart action occurring as one of the symptoms of exophthalmic goiter.
  • fetal t.: a fetal heart rate of 160 or more beats/min.
  • junctional t.: supraventricular t. arising from the atrioventricular junction (formerly called nodal t.).
  • multifocal atrial t.: atrial chaotic t..
  • nodal t.: atrioventricular junctional t..
  • orthostatic t.: increased heart rate on assuming the erect posture.
  • paroxysmal t.: recurrent attacks of t., usually with abrupt onset and often also abrupt termination, originating from an ectopic focus which may be atrial, AV junctional, or ventricular.
  • reflex t.: increased heart rate in response to some stimulus conveyed through the cardiac nerves.
  • sinus t.: t. originating in the sinus node.
  • supraventricular t.: rapid heart rate due to a pacemaker anywhere above the ventricular level, i.e., sinus node, atrium, atrioventricular junction. The QRS complexes are always narrow unless there is rate-related aberrancy or preexisting intraventricular conduction delay.
  • ventricular t.: paroxysmal t. originating in an ectopic focus in the ventricle. SEE ALSO: torsade de pointes.

    tachycardiac (tak-i-kar′de-ak)
    Relating to or suffering from excessively rapid action of the heart.

    tachycardic (tar-i-kar′dik)
    Relating to rapid heart rate.

    tachycrotic (tak′i-krot′ik)
    Relating to, causing, or characterized by a rapid pulse. [tachy- + G. krotos, a striking]

    tachykinin (tak-e-ki′nin)
    Any member of a group of polypeptides, widely scattered in vertebrate and invertebrate tissues, that have in common four of the five terminal amino acids: Phe–Xaa–Gly–Leu–Met–NH2; pharmacologically, they all cause hypotension in mammals, contraction of gut and bladder smooth muscle, and secretion of saliva. [G. tachys, swift, + kineo, to move, + -in]

    tachypacing (tak′i-pa′sing)
    Rapid pacing of the heart by an artificial electronic pacemaker operating faster than the basic cardiac rate.

    tachyphylaxis (tak′i-fi-lak′sis)
    Rapid appearance of progressive decrease in response to a given dose following repetitive administration of a pharmacologically or physiologically active substance. [tachy- + G. phylaxis, protection]

    tachypnea (tak-ip-ne′a)
    Rapid breathing. SYN: polypnea. [tachy- + G. pnoe (pnoie), breathing] transient t. of the newborn a syndrome of generally mild t. in otherwise healthy newborns, lasting usually only about 3 days. SYN: respiratory distress syndrome type II.

    tachyrhythmia (tak-i-ridh′me-a)
    SYN: tachycardia. [tachy- + G. rhythmos, rhythm]

    tachysterol (ta-kis′ter-ol)
    Sterol(s) formed by ultraviolet irradiation of any 5,7-diene-3β-sterol, which breaks the 9,10 bond, but usually from either or both of ergosterol and lumisterol to produce t.2 (ertacalciol, (6E,22E)-9,10-secoergosta-5(10),6,8,22-tetraen-3β-ol) and from 7-dehydrocholesterol to produce t.3 (tacalciol, (6E,3S)-9,10-secocholesta-5(10),6,8-trien-3β-ol). When reduced to the 5,7-diene (or 5,7,22-triene) form, dihydrotachysterol3 (10,19-dihydrocalciol) or dihydrotachysterol2 (10,19-dihydroercalciol), antirachitic action appears. This property has been of therapeutic interest, but t. is being replaced by the true vitamin D hormone (calcitriol) and its derivatives.

    tachysystole (tak-i-sis′to-le)
    SYN: tachycardia. [tachy- + G. systole, contracting]

    tachyzoite (tak-i-zo′it)
    A rapidly multiplying stage in the development of the tissue phase of certain coccidial infections, as in Toxoplasma gondii development in acute infections of toxoplasmosis. [tachy- + G. zoon, animal]

    tacrine (tak′ren)
    An anticholinesterase agent with nonspecific central nervous system stimulatory effects; used in early stages of Alzheimer disease.

    tactile (tak′til)
    Relating to touch or to the sense of touch. [L. tactilis, fr. tango, pp. tactus, to touch]

    taction (tak′shun)
    1. The sense of touch. 2. The act of touching. [L. tactio, fr. tango, pp. tactus, to touch]

    tactometer (tak-tom′e-ter)
    SYN: esthesiometer. [L. tactus, touch, + G. metron, measure]

    tactor (tak′tar, -tor)
    A tactile end organ. [L. one who or that which touches]

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