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Δ, δ

Uppercase and lowercase delta, respectively; the fourth letter of the Greek alphabet.


1. L. da, give; date; daughter; deciduous; L. detur, let it be given; dextrose; died; diopter; disability; divorced; doctor; drugs; permeability. 2. Symbol for the element deuterium.


loading dose.


deficient; density; L. dexter or dextro, right; L. dies, day; distal; dorsal; duration.


The first diagonal artery that branches off from the left anterior descending (LAD) coronary artery. Similarly, D2 is the second diagonal branch of the LAD.


In biochemistry, a prefix indicating the structure of certain organic compounds with asymmetric carbon atoms. If a carbon atom is attached to four different substituent groups that can be arranged in two ways and represent nonsuperimposable mirror images, it is classed as asymmetrical. The name of such a compound is preceded by D. When there are only three dissimilar groups around the carbon atom, only one configuration in space is possible. The carbon atom is classed as symmetrical (or chiral), and the name is preceded by L.

 In other chemical nomenclature, a lower-case d- or l- indicates the rotational direction of a polarized light shined through a solution of the compound. When the plane of the light is rotated to the right, i.e., is dextrorotatory, the compound’s name is preceded by d-. When the light is rotated to the left, i.e., is levorotatory, the name is preceded by l-.

 If a D compound that has an asymmetrical carbon can also rotate light and is dextrorotatory, its name is preceded by D(+); if levorotatory, by D(–). If the asymmetrical carbon is of the L form and is dextrorotatory, its name is prefixed by L(+); if it is levorotatory, the name is preceded by L(–).


digital to analog.




direct-acting antiviral.


[Gr. dakryon, a tear] Prefix meaning tears, lacrimal gland, lacrimal apparatus.


(dak″rē-ŏ-sis-tīt′ĭs) [dacrycyst + -it is] Inflammation of a lacrimal sac and its mucous and submucous membranes. It is usually secondary to prolonged obstruction of a nasolacrimal duct and may occasionally extend to the surrounding connective tissue and cause periorbital cellulitis.

 SYMPTOMS: The symptoms are epiphora (profuse tearing); redness and swelling in the lacrimal sac, which may also extend to the lids and conjunctiva; and pain, esp. on pressure over the sac.

 TREATMENT: Hot compresses should be applied to ...

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