Etymology
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conservant (adj.)

"having the power or quality of preserving from decay or destruction," 1580s, from Latin conservantem (nominative conservans), past participle of conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect").

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observatory (n.)

"building for observing astronomical phenomena," 1670s (in reference to Greenwich), from French observatoire, from observer (v.) "to observe, watch over, follow," from Latin observare "watch over," from ob "in front of, before" (see ob-) + servare "to watch, keep safe," from PIE root *ser- (1) "to protect."

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conserve (v.)

"to keep safe, preserve from loss or decay," late 14c., from Old French conserver (9c.), from Latin conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect"). Related: Conserved; conserving.

As a noun (often conserves) from late 14c. as "that which preserves;" early 15c. as "a confection, something preserved with sugar, etc."

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*ser- (1)

Proto-Indo-European root meaning "to protect." It forms all or part of: conservation; conservative; conserve; observance; observatory; observe; preserve; reservation; reserve; reservoir.

It is the hypothetical source of/evidence for its existence is provided by: Avestan haurvaiti "to guard;" Latin servare "to guard, keep, watch;" Old Church Slavonic xraniti "to guard, protect;" Old High German gi-sarwi "armor, equipment," Old English searu "art, skill; wile, deceit."

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reserve (v.)

mid-14c., "keep back or in store for future use;" late 14c., "keep as one's own," from Old French reserver "set aside, withhold" (12c.) and directly from Latin reservare "keep back, save up; retain, preserve," from re- "back" (see re-) + servare "to keep, save, preserve, protect" (from PIE root *ser- (1) "to protect"). Meaning "to book" is from 1935. Related: Reserved; reserving.

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observable (adj.)

c. 1600, "that must be attended, followed, or kept," also "worthy of notice or mention," from Latin observabilis "remarkable, observable," from observare "watch over, note, heed, look to, attend to, guard, regard, comply with," from ob "in front of, before" (see ob-) + servare "to watch, keep safe," from PIE root *ser- (1) "to protect." From 1640s as "perceptible, capable of being observed." Related: Observably; observability.

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reservoir (n.)

1680s, "a place where something tends to collect, place where anything is kept in store," originally figurative, from French réservoir "storehouse," from Old French reserver "set aside, withhold," from Latin reservare "keep back, save up; retain, preserve," from re- "back" (see re-) + servare "to keep, save, preserve, protect" (from PIE root *ser- (1) "to protect").

Specific meaning "capacious artificial basin to collect and store water" is from 1705. Earlier in this sense, and more common late 17c.-early 18c., was reservatory (1660s). Meaning "part of a machinery in which fluid is contained" is by 1784.

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observe (v.)

late 14c., observen, "to hold to (a manner of life or course of conduct), carry out the dictates of, attend to in practice, to keep, follow," from Old French observer, osserver "to observe, watch over, follow" (10c.), from Latin observare "watch over, note, heed, look to, attend to, guard, regard, comply with," from ob "in front of, before" (see ob-) + servare "to watch, keep safe," from PIE root *ser- (1) "to protect." Sense of "watch, perceive, notice" is from 1560s, via the notion of "see and note omens." Meaning "to say by way of remark" is from c. 1600. Related: Observed; observing.

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observation (n.)

late 14c., observacioun, "the performance of a religious rite," from Old French observation (c. 1200) and directly from Latin observationem (nominative observatio) "a watching over, observance, investigation," noun of action from past-participle stem of observare "watch over, note, heed, look to, attend to, guard, regard, comply with," from ob "in front of, before" (see ob-) + servare "to watch, keep safe," from PIE root *ser- (1) "to protect." Sense of "act or fact of paying attention" is from 1550s. Meaning "a remark in reference to something observed" is recorded from 1590s.

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conservancy (n.)

1755, "commission with jurisdiction over a port or river," from -cy + Latin conservant-, present-participle stem of conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect").

Earlier was conservacy "preservation under law, protection" (mid-15c., Anglo-French conservacie). The meaning "official preservation of undeveloped land" dates from 1859 (first reference is to the protection of bo trees in Ceylon). General sense of "act of preserving" is by 1832. Meaning "institution concerned with the preservation of nature, undeveloped land, etc." is by 1949.

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