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[hahy-drom-i-ter] /haɪˈdrɒm ɪ tər/
an instrument for determining the specific gravity of a liquid, commonly consisting of a graduated tube weighted to float upright in the liquid whose specific gravity is being measured.
Origin of hydrometer
1665-75; hydro-1 + -meter
Related forms
[hahy-druh-me-trik] /ˌhaɪ drəˈmɛ trɪk/ (Show IPA),
hydrometrical, adjective
hydrometry, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for hydrometer
  • There are no instruments to guide the process except several thermometers and a hydrometer.
  • The potato computer, the hydrometer, and the curing bins made it a science.
  • The hydrometer should bear an inscription that indicates the purpose of the instrument.
  • The hydrometer is gently lowered into the liquid to be measured until the hydrometer floats freely.
  • Salinity can be measured using a hydrometer or a refractometer.
  • The same hydrometer was placed in the liquids below.
  • First, a hydrometer test is performed which defines the fraction of sample that is silt and clay.
  • The brine solution flows into the holding tank and is tested for the correct concentration using a hydrometer or salimeter.
  • Keep the vent plugs in place at all times except when adding water to the cells or taking hydrometer readings.
  • Record the specific gravity with the hydrometer in the service log.
British Dictionary definitions for hydrometer


an instrument for measuring the relative density of a liquid, usually consisting of a sealed graduated tube with a weighted bulb on one end, the relative density being indicated by the length of the unsubmerged stem
Derived Forms
hydrometric (ˌhaɪdrəʊˈmɛtrɪk), hydrometrical, adjective
hydrometrically, adverb
hydrometry, noun
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
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Word Origin and History for hydrometer

1670s, from hydro- + meter (n.3).

Online Etymology Dictionary, © 2010 Douglas Harper
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hydrometer in Medicine

hydrometer hy·drom·e·ter (hī-drŏm'ĭ-tər)
An instrument used to determine specific gravity, especially a sealed graduated tube, weighted at one end, that sinks in a fluid to a depth indicating the fluid's specific gravity. Also called gravimeter.

hy'dro·met'ric (hī'drə-mět'rĭk) adj.
hy·drom'e·try n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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hydrometer in Science
An instrument used to measure the density of a liquid as compared to that of water. Hydrometers consist of a calibrated glass tube ending in a weighted glass sphere that makes the tube stand upright when placed in a liquid. The lower the density of the liquid, the deeper the tube sinks.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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