Glossary of Scientific Terms and Expressions: D

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A – B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S – T – U – V – W – X – Y – Z

  • declivity (de-KLEV-i-tee): L. declivis = bent or inclined downwards, sloping; 1. zool. anat. —sloping downward.
  • dentate (DEN-tat): L. dentatus = with teeth; 1. zool. anat. — toothed.
  • denticles (DEN-ti-kahls): L. denticulum = little tooth; 1. zool. anat. — small teeth.
  • diad (DYE-add): Gr. δι- “di” = pref. two-, double- + Gr. -αδ “ad” = suf. -‘to’, toward, near; 1. arach. anat. — a pair of two contiguous eyes.
  • diaxial (dye-AXE-ee-uhl) (= labidognathous, q.v.): L. dis– = pref. between, away from- + L. axis = an axle, axis; 1. arach. anat. — downward projecting chelicerae with the fangs operating along the transverse axis (functioning like ice hooks used to grasp and lift blocks of ice); present in Araneomorphae; compare with the orthogonal chelicerae of Mygalomorphae.
  • dichotomous (dye-KAH-tum-us) key: Gr. διχα “dicha” = in two, in two ways, asunder, apart, at variance; 1. zool. anat. — a listing of diagnostic characters for use in identifying organisms to various taxonomic levels, with the characters so arranged that gross characters are diagnosed first, whereupon successive diagnoses become more refined, following a process whereby each decision point offers the diagnostician two choices; on making a particular choice, the diagnostician either arrives at the organism’s identity, or is directed onward to one or more sets of alternative decision points.
  • digitiform (dij-IT-uh-fohrm): L. digitus = a finger or toe + L. forma = shape, form, beauty; 1. zool. anat. — finger-like.
  • dionychous (DYE-oh-NYE-kuhs): Gr. δι– “di” = pref. two-, double- + Gr. ονυξ “onych” = a talon, claw, nail, hoof; 1. arach. anat. — having two tarsal claws.
  • divergent (dye-VURG-unt): L. divertere = to turn different ways; mod. L., middle Fr.: proceeding in different directions from each other, or from a common point; departing more widely from one another; diverging; 1. zool. anat. — structures whose distance apart increases with distance from a point of relative proximity.
  • diverticula (DYE-vur-TIH-kyoo-lah): L. diverticulum = a by-way; 1. zool. anat. — extensions of the digestive system.
  • distal (DYS-tul) (also distad; = apical, apicad): L. distare, to stand apart; 1. zool. anat. — in the direction of the terminus of an appendage, away from the body.
  • distitarsus (DIS-teh-TAHR-suhs), pl. distitarsi: see tarsus.
  • dorsal (DOHR-sul) (also dorsad, dorsum): L. dorsum = the back, ridge, ledge; 1. zool. anat. — the upper surface, i.e., toward the top.
  • dorsal groove — see fovea.
  • dorsomesal (dohr-so-MEE-suhl): L. dorsum = the back, ridge, ledge + Gr. μεσος “mesos” = middle, in the middle; zool. anat. — toward the middle of the top of the body or appendage.



  • anat. = anatomy; arach. = arachnid; behav. = behavioral; biol. = biological (inclusive of all animals and plants); bot. = botanical (inclusive of all plants); Gr. = Greek; L. = Latin; q.v. = L. quod vide = which see; pl. = plural; taxon. = taxonomy; zool. = zoological (inclusive of all animals).



  • Allaby, Michael, Ed. 1991. The Concise Oxford Dictionary of Zoology. Oxford Press.
  • Beccaloni, Jan. 2009. Arachnids; Glossary, p. 319. University of California Press, p. 56.
  • Gertsch, Willis J., 1979. American Spiders, 2nd Edition: Glossary, pp. 255-260. Von Nostrand Reinhold Company.
  • Howell, W. Mike, and Ronald L. Jenkins. 2004. Spiders of the Eastern United States; Glossary, Chapter X, pp. 341-348. Pearson Education.
  • Jackman, John A. 1997. A Field Guide to Spiders & Scorpions of Texas: Glossary pp. 173-177. Texas Monthly.
  • Kaston, B. J. 1978. How to know the spiders: Index and Pictured Glossary, pp. 267-272. McGraw Hill Company.
  • Preston-Mafham, Rod. 1996. The Book of Spiders and Scorpions; Glossary, pp. 140-141. Barnes & Noble Books, New York.
  • Ubick, D., P. Paquin, P.E. Cusing and V. Roth, editors, 2005. Spiders of North America, Chapter 72: Glossary — pronunciation guide. Published by the American Arachnological Society.
  • Venes, Donald, Ed. 2009. Taber’s Cyclopedic Medical Dictionary, 21st Ed. F.A. Davis Company, Philadelphia.
  • Williams, Tim. 2005. A Dictionary of the Roots and Combining Forms of Scientific Words. Squirrox Press, Norfolk, England.

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