1. a single thing or person.
  2. any group of things or persons regarded as an entity: They formed a cohesive unit.
  3. one of the individuals or groups that together constitute a whole; one of the parts or elements into which a whole may be divided or analyzed.
  4. one of a number of things, organizations, etc., identical or equivalent in function or form: a rental unit; a unit of rolling stock.
  5. any magnitude regarded as an independent whole; a single, indivisible entity.
  6. Also called dimension. any specified amount of a quantity, as of length, volume, force, momentum, or time, by comparison with which any other quantity of the same kind is measured or estimated.
  7. the least positive integer; one.
  8. Also called unit's place.
    1. (in a mixed number) the position of the first digit to the left of the decimal point.
    2. (in a whole number) the position of the first digit from the right of the decimal point.
  9. a machine, part, or system of machines having a specified purpose; apparatus: a heating unit.
  10. Education. a division of instruction centering on a single theme.
  11. Military. an organized body of soldiers, varying in size and constituting a subdivision of a larger body.
  12. Medicine/Medical.
    1. the measured amount of a substance necessary to cause a certain effect; a clinical quantity used when a substance cannot be readily isolated in pure form and its activity determined directly.
    2. the amount necessary to cause a specific effect upon a specific animal or upon animal tissues.
  13. Mathematics.
    1. an identity element.
    2. an element in a group, ring, etc., that possesses an inverse.

Origin of unit

1570; coined by John Dee as a translation of Greek mónas (previously rendered as unity); perhaps influenced by digit
Related formsin·ter·u·nit, adjectivemul·ti·u·nit, adjectivesub·u·nit, nounsu·per·u·nit, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for multiunit


  1. a single undivided entity or whole
  2. any group or individual, esp when regarded as a basic element of a larger whole
  3. a mechanical part or integrated assembly of parts that performs a subsidiary functiona filter unit
  4. a complete system, apparatus, or establishment that performs a specific functiona production unit
  5. a subdivision of a larger military formation
  6. Also called: unit of measurement A standard amount of a physical quantity, such as length, mass, energy, etc, specified multiples of which are used to express magnitudes of that physical quantitythe second is a unit of time
  7. the amount of a drug, vaccine, etc, needed to produce a particular effect
  8. a standard measure used in calculating alcohol intake and its effect
  9. maths
    1. (usually plural)the first position in a place-value counting system, representing a single-digit numberin the decimal system the number 27 has 7 units and 2 tens
    2. (modifier)having a value defined as one for the systemunit vector
  10. Also called: unit set maths logic a set having a single member
  11. short for home unit
  12. short for stock unit
  13. NZ a self-propelled railcar

Word Origin for unit

C16: back formation from unity, perhaps on the model of digit
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for multiunit



1560s, "single number regarded as an undivided whole," alteration of unity on the basis of digit. Popularized in John Dee's English translation of Euclid, to express Greek monas (Dee says unity formerly was used in this sense). Meaning "single thing regarded as a member of a group" is attested from 1640s. Extended sense of "a quantity adopted as a standard of measure" is from 1738. Sense of "group of wards in a hospital" is attested from 1893.

Online Etymology Dictionary, © 2010 Douglas Harper

multiunit in Medicine


  1. An entity regarded as an elementary structural or functional constituent of a whole.
  2. A precisely specified quantity in terms of which the magnitudes of other quantities of the same kind can be stated.
  3. The quantity of a serum, drug, or other agent necessary to produce a specific effect.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.