Etymology
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similar (adj.)

"having characteristics in common," 1610s (earlier similary, 1560s), from French similaire, from a Medieval Latin extended form of Latin similis "like, resembling, of the same kind," from Old Latin semol "together" (from PIE root *sem- (1) "one; as one, together with"). The noun meaning "that which is similar" is from 1650s. Related: Similarly.

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similarity (n.)
"state of being similar," 1660s, from similar + -ity, or from French similarité. Related: Similarities "points of resemblance" (1838).
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dissimilar (adj.)

"unlike in appearance, properties, or nature," 1620s, from dis- + similar; perhaps on analogy of French dissimilaire. Related: Dissimilarity.

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similitude (n.)
late 14c., from Old French similitude "similarity, relationship, comparison" (13c.) and directly from Latin similitudinem (nominative similitudo) "likeness, resemblance," from similis "like, resembling, of the same kind" (see similar).
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simular (n.)
1520s, "one who simulates," irregularly formed (perhaps on the model of similar) from Latin simulare "to make like, imitate, copy, represent," from stem of similis "like, resembling, of the same kind" (see similar). As an adjective, "simulated," from 1610s.
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simile (n.)
late 14c., from Latin simile "a like thing; a comparison, likeness, parallel," neuter of similis "like, resembling, of the same kind" (see similar). Both things must be mentioned and the comparison directly stated. To Johnson, "A simile, to be perfect, must both illustrate and ennoble the subject."
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simulator (n.)
1835, of persons, from Latin simulator "a copier, feigner," agent noun from simulare "to make like, imitate, copy, represent," from stem of similis "like, resembling, of the same kind" (see similar). In reference to training devices for complex systems, from 1947 (flight simulator).
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facsimile (n.)

"exact copy," 1690s, two words, from Latin fac simile "make similar," from fac imperative of facere "to make" (from PIE root *dhe- "to set, put") + simile, neuter of similis "like, resembling, of the same kind" (see similar). One-word form predominated in 20c. As an adjective from 1877.

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simulacrum (n.)

1590s, from Latin simulacrum "likeness, image, form, representation, portrait," a dissimilation of *simulaclom, from simulare "to make like, imitate, copy, represent," from stem of similis "like, resembling, of the same kind" (see similar). The word was borrowed earlier as semulacre (late 14c.), via Old French simulacre.

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verisimilitude (n.)
"appearance of truth or reality, likelihood," c. 1600, from French verisimilitude (1540s), from Latin verisimilitudo "likeness to truth," from veri, genitive of verum, neuter of verus "true" (from PIE root *were-o- "true, trustworthy") + similis "like, resembling, of the same kind" (see similar). Related: Verisimilar.
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