1. The act of measuring or the process of being measured.
2. A system of measuring: measurement in miles.
3. The dimension, quantity, or capacity determined by measuring: the measurements of a room.
CONVERSION BETWEEN METRIC AND U.S. CUSTOMARY UNITS
FROM U.S. CUSTOMARY TO METRIC
FROM METRIC TO U.S. CUSTOMARY
TEMPERATURE CONVERSION BETWEEN CELSIUS AND FAHRENHEIT
UNITS OF THE INTERNATIONAL SYSTEM
The International System (abbreviated SI, for Système International, the French name for the system) was adopted in 1960 by the 11th General Conference on Weights and Measures. An expanded and modified version of the metric system, the International System addresses the needs of modern science for additional and more accurate units of measurement. The key features of the International System are decimalization, a system of prefixes, and a standard defined in terms of an invariable physical measure.
The International System has base units from which all others in the system are derived. The standards for the base units, except for the kilogram, are defined by unchanging and reproducible physical occurences. For example, the meter is defined as the distance traveled by light in a vacuum in 1/299,792,458 of a second. The standard for the kilogram is a platinum-iridium cylinder kept at the International Bureau of Weights and Standards in Sèvres, France.
A multiple of a unit in the International System is formed by adding a prefix to the name of that unit. The prefixes change the magnitude of the unit by orders of ten from 1024 to 10-24.
Most of the units in the International System are derived units, that is units defined in terms of base units and supplementary units. Derived units can be divided into two groups—those that have a special name and symbol, and those that do not.
Copyright © 2011 by Houghton Mifflin Harcourt Publishing Company
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.