1660s, in biology, "unable to support itself, lying on the ground without putting forth roots," from Latin procumbentem (nominative procumbens), present participle of procumbere "to fall forward, fall prostrate," from pro "forward" (see pro-) + -cumbere "take a reclining position," related to cubare "lie down" (see cubicle). The meaning "leaning forward, lying on the face" is from 1721. Related: Procumbently.
"distorted projection or drawing" (one that looks normal from a particular angle or with a certain mirror), 1727, from Greek anamorphosis "transformation," noun of action from anamorphoein "to transform," from ana "up" (see ana-) + morphosis, from morphe "form," a word of uncertain etymology. In botany, "monstrous development of a part" (1830); in evolutionary biology, "gradual change of form in a species over time" (1852).
mid-15c. (late 13c., Anglo-French), receptour, "a knowing harborer of criminals, heretics, etc.," from Old French receptour or directly from Latin receptor, agent noun from recipere "to hold, contain" (see receive). Molecular biology sense is from 1900. Compare receiver. A receptory (early 15c., from Medieval Latin) was, among other definitions, an alchemical flask for receiving distillates.
1833, in biology, "reversion by influence of heredity to ancestral characteristics, resemblance of a given organism to some remote ancestor, return to an early or original type," from French atavisme, attested by 1820s, said to have been coined by French botanist Antoine-Nicolas Duchesne, from Latin atavus "ancestor, forefather," from at- perhaps here meaning "beyond" + avus "grandfather," from PIE *awo- "adult male relative other than the father" (see uncle).
late 14c., from Greek hamadryas (plural hamadryades) "wood-nymph," fabled to die with her tree, from hama "together with" (from PIE root *sem- (1) "one; as one, together with") + dryas (plural dryades) "wood nymph," from drus (genitive dryos) "tree," especially "oak" (from PIE root *deru- "be firm, solid, steadfast," with specialized senses "wood, tree"). Use in 19c. biology for a type of butterfly, a type of venomous Indian serpent, and a type of large hairy baboon.
1650s, euphemism for "underground sewer," from Latin cloaca "public sewer, drain," from cluere "to cleanse," probably from PIE root *kleu- "to wash, clean" (source also of Greek klyzein "to dash over, wash off, rinse out," klysma "liquid used in a washing;" Lithuanian šluoju, šluoti "to sweep;" Old English hlutor, Gothic hlutrs, Old High German hlutar, German lauter "pure, clear"). Use in biology, in reference to eliminatory systems of lower animals, is from 1834. Related: Cloacal (1650s); cloacinal (1857).
1704, "kernel of a nut;" 1708, "head of a comet;" from Latin nucleus "kernel," from nucula "little nut," diminutive of nux (genitive nucis) "nut," from PIE *kneu- "nut" (source also of Middle Irish cnu, Welsh cneuen, Middle Breton knoen "nut," Old Norse hnot, Old English hnutu "nut").
The general sense of "central mass or thing, about which others cluster or matter collects," is from 1762. In biology, "dense, typically rounded structure in a cell, bounded by membranes," from 1831. Later they were found to contain the genetic material. Modern meaning in physics, "positively charged central core of an atom," is from 1912, by Ernest Rutherford, though theoretical use for "central point of an atom" is from 1844, in Faraday.
1879, from Latin optimum, neuter singular of optimus "best, very good" (used as a superlative of bonus "good"), perhaps (Watkins) related to ops "power, resources" (in which case the evolution is from "richest" to "the most esteemed," thus from PIE root *op- "to work, produce in abundance"); or perhaps it is related to ob "in front of" (de Vaan), with superlative suffix *-tumos.
In English the word was used originally in biology, in reference to "conditions most favorable" (for growth, metabolic processes, etc.). As an adjective, "best or most favorable," from 1885.