Etymology
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indication (n.)

early 15c., "a sign, that which indicates," from Latin indicationem (nominative indicatio) "an indicating; valuation," noun of action from past participle stem of indicare "point out, show," from in- "into, in, on, upon" (from PIE root *en "in") + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction).

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coindication (n.)

also co-indication, "a concurrent sign or symptom," 1620s, from co- + indication.

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indicator (n.)
1660s, "that which indicates or points out," from Late Latin indicator, agent noun from indicare "to point out, show" (see indication). As a finger muscle, from 1690s. As a steam-cylinder's pressure gauge, 1839. As a device on a motor vehicle to signal intention to change direction, 1932.
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indicate (v.)

1650s, "to point out," back-formation from indication (q.v.) or else from Latin indicatus, past participle of indicare "to point out, show," from in- "into, in, on, upon" (from PIE root *en "in") + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction). Especially "to give suggestion of, be reason for inferring" (1706). Related: Indicated; indicating.

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indicative (adj.)

mid-15c., "that points out, states, or declares" (grammatical), from Old French indicatif (14c.), from Late Latin indicativus "serving to point out," from indicat-, past participle stem of Latin indicare "to point out, show" (see indication). The "mood in the conjugation of a Latin verb whose essential function is to state a fact (as opposed to a wish, supposition or command)" [The Middle English Compendium]. Related: Indicatively.

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*deik- 
Proto-Indo-European root meaning "to show," also "pronounce solemnly," "also in derivatives referring to the directing of words or objects" [Watkins].

It forms all or part of: abdicate; abdication; addict; adjudge; apodictic; avenge; benediction; betoken; condition; contradict; contradiction; dedicate; deictic; deixis; dictate; diction; dictionary; dictum; digit; disk; ditto; ditty; edict; Eurydice; index; indicate; indication; indict; indiction; indictive; indite; interdict; judge; judicial; juridical; jurisdiction; malediction; malison; paradigm; policy (n.2) "written insurance agreement;" preach; predicament; predicate; predict; prejudice; revenge; soi-disant; syndic; teach; tetchy; theodicy; toe; token; valediction; vendetta; verdict; veridical; vindicate; vindication; voir dire.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dic- "point out, show;" Greek deiknynai "to show, to prove," dike "custom, usage;" Latin dicere "speak, tell, say," digitus "finger," Old High German zeigon, German zeigen "to show," Old English teon "to accuse," tæcan "to teach."
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omen (v.)

"to give indication of the future," 1775, from omen (n.). Related: Omened. The Latin verb ominari meant "to know or tell from omens, to predict."

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dateless (adj.)

1640s, "having no indication of time," from date (n.1) + -less. From 1923 as "free from engagements or appointments," from date (n.3).

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deixis (n.)

"indication, pointing out," 1949, in grammar, from Greek deixis "reference," from deiknynai "to show" (from PIE root *deik- "to show"). Related: Deictic.

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flatline (v.)
"give no indication of life, cease to function," by 1998, from the flat (adj.) line (n.) on an electrocardiogram or electroencephalogram when the patient is dead. Related: Flatlined; flatlining.
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