late 14c., "not whole or total, incomplete;" early 15c., "one-sided, biased, inclined to favor one party in a cause or one side of a question more than the other," also "pertaining to a selfish interest rather than to a common or larger good," from Old French parcial (14c., Modern French partial) and directly from Medieval Latin partialis "divisible, solitary, partial," from Latin pars (genitive partis) "a part, piece, a share, a division" (from PIE root *pere- (2) "to grant, allot").
Weakened sense of "favorably disposed" is from 1580s. Meaning "affecting a part only, not universal or general" is by 1640s.
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).
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Definitions of partialness
the state of being only a part; not total; incomplete;