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The Collaborative International Dictionary
Imperfect number

Imperfect \Im*per"fect\, a. [L. imperfectus: pref. im- not + perfectus perfect: cf. F imparfait, whence OE. imparfit. See Perfect.]

  1. Not perfect; not complete in all its parts; wanting a part; deective; deficient.

    Something he left imperfect in the state.
    --Shak.

    Why, then, your other senses grow imperfect.
    --Shak.

  2. Wanting in some elementary organ that is essential to successful or normal activity.

    He . . . stammered like a child, or an amazed, imperfect person.
    --Jer. Taylor.

  3. Not fulfilling its design; not realizing an ideal; not conformed to a standard or rule; not satisfying the taste or conscience; esthetically or morally defective.

    Nothing imperfect or deficient left Of all that he created.
    --Milton.

    Then say not man's imperfect, Heaven in fault; Say rather, man's as perfect as he ought.
    --Pope.

    Imperfect arch, an arch of less than a semicircle; a skew arch.

    Imperfect cadence (Mus.), one not ending with the tonic, but with the dominant or some other chord; one not giving complete rest; a half close.

    Imperfect consonances (Mus.), chords like the third and sixth, whose ratios are less simple than those of the fifth and forth.

    Imperfect flower (Bot.), a flower wanting either stamens or pistils.
    --Gray.

    Imperfect interval (Mus.), one a semitone less than perfect; as, an imperfect fifth.

    Imperfect number (Math.), a number either greater or less than the sum of its several divisors; in the former case, it is called also a defective number; in the latter, an abundant number.

    Imperfect obligations (Law), obligations as of charity or gratitude, which cannot be enforced by law.

    Imperfect power (Math.), a number which can not be produced by taking any whole number or vulgar fraction, as a factor, the number of times indicated by the power; thus, 9 is a perfect square, but an imperfect cube.

    Imperfect tense (Gram.), a tense expressing past time and incomplete action.

Usage examples of "imperfect number".

And so we shall say that men were made not only to restore the diminished number, but also to complete the imperfect number.