Glossary of Scientific Terms and Expressions: A

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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

  • abdomen (AB-doh-mun): L. abdomen = the belly; 1. zoology — a. vertebrates — the body region containing the internal organs other than the heart and lungs (in Mammalia: bounded by diaphragm); 2. arthropods — the hind region (tagma) of the body containing most of the digestive tact, the gonads, and the genital openings; 2a. arachnids — the posterior division of the spider body (= opisthosoma, q.v.), comprising the pedicel and usu. largely unsegmented sac-like portion bearing posteriorly the spinnerets; 2b. Insects — the segments of the body lying posterior to the thorax.
  • accessory claws: 1. arachnids — serrated setae on the distal tarsi of web-building spiders, used to grip the silk line.
  • aciniform (uh-SIN-i-form): 1. arachnids — one of six kinds of silk glands found in spiders. See also ampullate, tubuliform, aggregate, piriform, and flagelliform, or coronate.
  • acuminate (uh-KYOO-men-ate): L. acumen = a sharp point, a point, cunning + L. at = before, at, towards: 1. zoology — tapering to a point.
  • AER: 1. arachnids — acronymic desig. for anterior eye row.
  • aggressive mimicry: 1. arachnids — spider predation on other spiders, via the stratagem of approaching the other’s web, vibrating it as would a snared insect, then attacking the web’s occupant when the latter approaches to investigate.
  • ALE: 1. arachnids — acronymic desig. for anterior lateral eye, i.e., the lateral-most eye of the AER (q.v.).
  • agonistic (AAG-oh-NISS-tick): Gr. αγων “agon” = assembly, contest, struggle; also Gr. αγωνιστης “agonistes” = champion: 1. zoology — combative or aggressive behavior.
  • alveolus (al-vee-OH-luhs): L. alveolus = small pit, cavity, socket; 1. arachnids — the concave ventral surface of the male palpal cymbium, i.e., the modified palpal tarsus wherein resides the genital bulb (q.v.).
  • AME: 1. arachnids — acronymic desig. for anterior median eye(s), i.e., the mid-most eye(s) of the AER (q.v.).
  • anal tubercle (AA-nul TUU-burr-kul): 1. arachnids — a small caudal tubercle, posterior to a spider’s spinnerets, that bears the anal opening, also known as the post-abdomen.
  • angulate (AN-ghu-late): L. angulus = a corner, angle; 1. zoology — having an angular form.
  • annulate (AN-yoo-late): L. annulus = a signet ring, or more generally, a ring; 1. arachnids — transverse rings of pigmentation around a body part such as a leg.
  • annuli (AN-yoo-lye): L. annulus = a signet ring, or more generally, a ring; 1. arachnids — transverse wrinkles, or rings, on an epigynal scape or other anatomical structure.
  • anteriad (an-TEER-ee-ud) (= anterior, [q.v.]): L. anterius = before, in front of, former + L. –ad = toward;  1. biology — toward the front.
  • anterior (an-TEER-ee-ohr) (= anteriad): L. anterius = before, in front of, former; 1. biology — the front, toward the front.
  • anterior eye row (AER): 1. arachnids — the anteriormost row of eyes, usu. comprising the anterior lateral eyes (ALE) and anterior median eyes (AME).
  • anterior lateral eye(s) (ALE): 1. arachnids; 1.a. spiders — eyes situated on the anterolateral portion of the eye group.
  • anterior lateral spinnerets (ALS) = anterior spinnerets: 1. arachnids; 1.a. spiders — anterolateral spinnerets, as distinguished from the anteromedial spinnerets (q.v.); these are large in the Araneomorphae, but are absent in most Mygalomorphae.
  • anterior median eyes (AME) (= primary eyes, q.v.): 1. arachnids; 1.a. spiders — eyes situated at the anteromedial portion of the eye group; morphologically distinct from the other eyes, and often reduced or lost.
  • anterior median spinnerets (AMS) = anteromedial spinnerets: 1. arachnids; 1.a. spiders — distinguished from the anterior lateral spinnerets (ALS) (q.v.); these are present only in some Mesothelae, absent in Mygalomorphae, and represented by a cribellum or colulus in Araneomorphae.
  • anterior spinnerets = anterior lateral spinnerets (q.v.)
  • anterodorsal: 1. zoology — toward the front of the dorsal, or top, surface of the body, appendage, or other anatomical structure.
  • anterolateral: 1. zoology — toward the front side portion of the body, appendage, or other anatomical structure.
  • anteromesal: 1. zoology — toward the midline front of a body, appendage, or other anatomical structure.
  • anteroventral: 1. zoology — toward the front of the ventral, or underside, of a body, appendage, or other anatomical structure.
  • apical (AP-i-kuhl) (also apicad) = distal (distad): 1. zoology — toward the terminus of an appendage, away from the body.
  • apodeme (AP-oh-deem): Gr. απο “apo” = out of, away from + Gr. δεμας “demas”= the living body; 1. zoology — an external skeletal process.
  • apomorphic (ap-oh-MOHR-fik): Gr. απο “apo” = out of, away from + Gr. μορφη “morphe” = form, shape, figure, thus the derivative of a (more primitive) structure; 1. zoology — derived, advanced.
  • apophysis (uh-PAH-fuh-sis); pl. apophyses: Gr. απο “apo” = out of, away from + Gr. φυσις “physis” = origin, the natural form or constitution, outward form, natural place, one’s nature, thus a protrusion emanating from an anatomical structure; 1. arachnids; 1.a. spiders — a cuticular or sclerotized projection (evagination), common on male palpal segments, including femur, patella, or tibia, of the palp.
  • Arachnida (uh-RAKH-nud-uh): 1. arachnids — a class of arthropods first described by Jean Léopold Nicolas Frédéric Cuvier [August 23, 1769 – May 13, 1832], a.k.a. Georges Cuvier, a French naturalist and zoologist, in 1812, using the Gr. noun αραχης “araches” = a spider, in reference to all eight-legged arthropods, including such disparate animals as ticks, mites, scorpions, harvestmen, solpugids, and spiders.
  • Araneae (uh-RAIN-ee-uh): 1. arach. taxon. — an order of arachnids(described by Carl Alexander Clerck [1709 – 22 July 1765], a Swedish entomologist and arachnologist, in 1757, using the L. aranea = a spider or a spider’s web, to refer to eight legged arthropods that spin webs.
  • Araneomorphae (uh-RAIN-ee-oh-MOHR-fee) (= the true spiders): L. aranea = a spider or a spider’s web + Gr. μορφωσις = “morphosis” = shaping, semblance, form; 1. arachnids; 1.a. spiders — one of two infraorders of spiders (see also Mygalomorphae) comprised of most modern spiders, including the orbweavers, wolf spiders, jumping spiders, etc.
  • arboreal (Ahrr-buh-REE-uhl): L. arbor = a tree + –eal, a prepositional combining form → of trees; 1. zoology — tree dwelling.
  • arcuate (AHR-kyoo-at): L. arcus = a bow; also L. arcuatus = curved; + L. at = at, to, towards; 1. zoology — curved like a bow or arc-shaped.
  • Arthropoda.
  • attenuate (ah-TEN-yoo-utt):  L. attenuatus = weakened, meagre, unadorned; 1. zoology — tapering into a long point.
  • atriobursal (Ate-ree-oh-BUHR-suhl) orifice: 1. arachnids; 1.a. spiders — the opening of the seminal receptacle of a female spider.
  • atrium (AA-tree-uhm): L. atrium = an entrance hall; 1. arachnids; 1.a. spiders — the enlarged opening in the gonopore in haplogyne females; a cavity in the epigynal plate of entelegyne females containing copulatory openings.
  • autospasy (ah-toh-SPAY-see) = autotomize, autotomy: Gr. αυτος “autos” = self + Gr. σπαω “spao” = pluck off, tear, drag away; 1. zoology — the sacrificial loss of a leg or other appendage at a locus of contrived weakness, usu. as a means of defense against predators; in spiders this often occurs at the coxa-trochanter joint, but sometimes takes place at the patella-tibia joint; in anurans this often occurs at the suture where the tail attaches to the body.
  • autotomize (aw-TAW-toh-meyz) = autospasyautotomy: Gr. αυτος “autos” = self + Gr. τομις “tomis” = knife, thus a willful self-removal or excision; 1. zoology — intentional removal, or breaking off, by a spider, of its own 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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