tactic (n.)

1766, from Modern Latin tactica, from Greek taktikē (tekhnē) "(art of) arrangement," from fem. of taktikos "pertaining to arrangement" (see tactics). Earlier it meant "a tactician" (1630s), and was in use as an adjective meaning "tactical" (c. 1600).

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science (n.)
Origin and meaning of science

mid-14c., "state or fact of knowing; what is known, knowledge (of something) acquired by study; information;" also "assurance of knowledge, certitude, certainty," from Old French science "knowledge, learning, application; corpus of human knowledge" (12c.), from Latin scientia "knowledge, a knowing; expertness," from sciens (genitive scientis) "intelligent, skilled," present participle of scire "to know."

The original notion in the Latin verb probably is "to separate one thing from another, to distinguish," or else "to incise." This is related to scindere "to cut, divide" (from PIE root *skei- "to cut, split;" source also of Greek skhizein "to split, rend, cleave," Gothic skaidan, Old English sceadan "to divide, separate").

OED writes that the oldest English sense of the word now is restricted to theology and philosophy. From late 14c. in English as "book-learning," also "a particular branch of knowledge or of learning, systematized knowledge regarding a particular group of objects;" also "skillfulness, cleverness; craftiness." From c. 1400 as "experiential knowledge;" also "a skill resulting from training, handicraft; a trade."

From late 14c. in the more specific sense of "collective human knowledge," especially that gained by systematic observation, experiment, and reasoning. The modern (restricted) sense of "body of regular or methodical observations or propositions concerning a particular subject or speculation" is attested by 1725; in 17c.-18c. this commonly was philosophy.

The sense of "non-arts studies" is attested from 1670s. The distinction is commonly understood as between theoretical truth (Greek epistemē) and methods for effecting practical results (tekhnē), but science sometimes is used for practical applications and art for applications of skill.

The predominant modern use, "natural and physical science," generally restricted to study of the phenomena of the material universe and its laws, is by mid-19c.

To blind (someone) with science "confuse by the use of big words or complex explanations" is attested from 1937, originally noted as a phrase from Australia and New Zealand. 

The men who founded modern science had two merits which are not necessarily found together: Immense patience in observation, and great boldness in framing hypotheses. The second of these merits had belonged to the earliest Greek philosophers; the first existed, to a considerable degree, in the later astronomers of antiquity. But no one among the ancients, except perhaps Aristarchus, possessed both merits, and no one in the Middle Ages possessed either. [Bertrand Russell, "A History of Western Philosophy," 1945] 
Science, since people must do it, is a socially embedded activity. It progresses by hunch, vision, and intuition. Much of its change through time does not record a closer approach to absolute truth, but the alteration of cultural contexts that influence it so strongly. Facts are not pure and unsullied bits of information; culture also influences what we see and how we see it. Theories, moreover, are not inexorable inductions from facts. The most creative theories are often imaginative visions imposed upon facts; the source of imagination is also strongly cultural. [Stephen Jay Gould, introduction to "The Mismeasure of Man," 1981]
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science fiction (n.)

1929 (in advertisements for "Air Wonder Stories" magazine), though there is an isolated use from 1851. See science + fiction. Earlier in same sense was scientifiction (by 1926). Abbreviated form sci-fi is by 1955. 

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pseudo-science (n.)

also pseudoscience, "a pretended or mistaken science," 1796 (the earliest reference is to alchemy), from pseudo- + science.

The term pseudo-science is hybrid, and therefore objectionable. Pseudognosy would be better etymology, but the unlearned might be apt to association with it the idea of a dog's nose, and thus, instead of taking "the eel of science by the tail," take the cur of science by the snout; so that all things considered we had better adopt the current term pseudo-sciences ["The Pseudo-Sciences," in The St. James's Magazine, January 1842]
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tactician (n.)
"expert in tactics," 1761, from tactic + -ian.
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reductio ad absurdum 
Latin, literally "reduction to the absurd." Absurdum is neuter of absurdus. See reduction + absurd. The tactic is useful and unobjectionable in proofs in geometry.
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firebomb (n.)
also fire-bomb, 1895 (earlier as a type of fireworks and a type of cannonball), from fire (n.) + bomb (n.). As a verb, from 1950 as an act of vandalism or terrorism, from 1941 as a military aviation tactic. Related: Firebombed; firebombing.
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physics (n.)

1580s, "natural science, the science of the principles operative in organic nature," from physic in sense of "natural science." Also see -ics. Based on Latin physica (neuter plural), from Greek ta physika, literally "the natural things," title of Aristotle's treatise on nature. The current restricted sense of "science treating of properties of matter and energy" is from 1715.

Before the rise of modern science, physics was usually defined as the science of that which is movable, or the science of natural bodies. It was commonly made to include all natural science. At present, vital phenomena are not considered objects of physics, which is divided into general and applied physics. [Century Dictionary, 1895]
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gunnery (n.)
c. 1600, "science of gun-making," from gun + -ery. Meaning "science of firing guns" is from 1816.
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in reference to solid-fuel rockets (1809) or matches (1839), a reference to English inventor Sir William Congreve (1772-1828), who learned the tactic of rocket warfare while serving in India. He was a descendant of the family of William Congreve the Restoration playwright (1670-1729), being probably his great-great-nephew.

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