Etymology
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remanent (adj.)

early 15c., "remaining, left over; left behind, remaining, continuing, staying," senses now obsolete, from Old French remanant, remenant, present-participle of remanoir "to stay; be left," and directly from Latin remanentem (nominative remanens), present participle of remanere "stay behind; be left behind" (see remain (v.), and compare remnant, which is a syncopated version of this word). In physics by 1866, probably from Latin.

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radiation (n.)

mid-15c., radiacion, "act or process of emitting light," from Latin radiationem (nominative radiatio) "a shining, radiation," noun of action from past-participle stem of radiare "to beam, shine, gleam; make beaming," from radius "beam of light; spoke of a wheel" (see radius).

Meaning "rays or beams emitted" is from 1560s. Meaning "divergence from a center" is 1650s. In modern physics, "emission or transmission of energy in the form of waves or particles," especially in reference to ionizing radiation, from early 20c.

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indium (n.)
metallic element, 1864, Modern Latin, from indicum "indigo" (see indigo) + chemical name element -ium. So called for its spectral lines. Ferdinand Reich (1799-1882), professor of physics at Freiberg, isolated it while analyzing local zinc ores in 1863 and identified it as a new element by the two dark blue lines in its spectrum, which did not correspond to any known element. The discovery had to be observed by his assistant, Theodor Richter, because Reich was color-blind.
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mega- 

before vowels meg-, word-forming element often meaning "large, great," but in physics a precise measurement to denote the unit taken a million times (megaton, megawatt, etc.), from Greek megas "great, large, vast, big, high, tall; mighty, important" (fem. megale), from PIE root *meg- "great." Mega began to be used alone as an adjective by 1982.

High-speed computer stores 2.5 megabits [headline in "Electronics" magazine, Oct. 1, 1957]
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plasma (n.)

1712, "form, shape" (a sense now obsolete), a more classical form of earlier plasm; from Late Latin plasma, from Greek plasma "something molded or created," hence "image, figure; counterfeit, forgery; formed style, affectation," from plassein "to mold," originally "to spread thin," from PIE *plath-yein, from root *pele- (2) "flat; to spread."

Sense of "the liquid part of blood, etc., as distinguished from the corpuscles" is from 1845. In physics, the sense of "ionized gas" is by 1928.

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proton (n.)

1920 in physics sense of "sub-atomic particle with a positive charge," coined by British physicist Ernest Rutherford (1871-1937) from noun use of Greek prōton, neuter of prōtos "first" (see proto-), on analogy of electron; supposedly because hydrogen (the nucleus of which, in its commonest form, consists of one proton) was hypothesized as a constituent of all the elements. The word was used earlier in embryology (1893) as a translation of German anlage ("fundamental thing") based on Aristotle's phrase he prote ousia to proton.

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core (n.)

early 14c., "heart or inmost part of anything" (especially an apple, pear, etc.), of uncertain origin, probably from Old French cor, coeur "core of fruit, heart of lettuce," literally "heart," from Latin cor "heart," from PIE root *kerd- "heart."

Meaning "a central portion cut and removed" (as from a tree, soil, etc.) is from 1640s. Meaning "internal mold of a casting, which fills the space intended to be left hollow" is from 1730. Nuclear physics sense "portion of a reactor containing the nuclear fuel and where the reactions take place" is from 1949.

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eugenics (n.)

"doctrine of progress in evolution of the human race, race-culture," 1883, coined (along with adjective eugenic) by English scientist Francis Galton (1822-1911) on analogy of ethics, physics, etc. from Greek eugenes "well-born, of good stock, of noble race," from eu- "good" (see eu-) + genos "birth" (from PIE root *gene- "give birth, beget").

The investigation of human eugenics, that is, of the conditions under which men of a high type are produced. [Galton, "Human Faculty," 1883]
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Maxwell 

surname, later masc. proper name, attested from late 12c., from Maxwell, name of a town on the River Tweed on the Scottish borders (the name is probably "the well of Macc or Macca"). In physics, usually a reference to James Clerk Maxwell (1831-1879), as in Maxwell's demon (1879; as Maxwell's "intelligent demons" from 1874).

The definition of a "demon," according to the use of this word by Maxwell, is an intelligent being endowed with free will, and fine enough tactile and perceptive organisation to give him the faculty of observing and influencing individual molecules of matter. ["Nature," April 9, 1874]
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fusion (n.)

1550s, "act of melting by heat," from French fusion or directly from Latin fusionem (nominative fusio) "an outpouring, effusion," noun of action from fusus, past participle of fundere "to pour, melt" (from nasalized form of PIE root *gheu- "to pour"). Meaning "union or blending of different things; state of being united or blended" is by 1776; used especially in 19c, of politics, in early 20c. of psychology, atoms, and jazz (in nuclear physics sense, first recorded 1947; in musical sense, by 1972).

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