Units of Measurement are part of the civilizations of human being, they not only reflect their diverse roots in Celtic, Roman, Saxon, and Norse cultures in Europe, but also record the different cultural connections in the Middle East, India, China and Asian Nations.

One of the earliest types of measurement might be the length. These measurements were usually based on parts of the body.  By 2500 BC,  the Egyptian  had standardized their royal master units of measurement  like cubit which represented the length of a man's forearm from his elbow to the tip of his outstretched middle finger. As early as 200 BC, the first emperor of the Chin Dynasty in ancient China, had established the uniformity in Measurement (including length, area, weight, and volume) throughout the Empire. And all different nations had their own units varied in region to meet their needs in life.

The French Metric System brought order out of the conflicting and confusing traditional systems of weights and measures, then being used in Europe in the 1790's. Prior to its introduction, it was common for units of length, land area, and weight to vary, not just from one country to another but from one region to another within the same country.  In England, units of measurement were not properly standardized until the 13th century, though variations continued until long after that. For example, there were three different gallons (ale, wine and corn) up until 1824 when the gallon was standardized.

Around 1850,  a strong movement began among scientists, engineers, and businessmen in favor of a international system of weights and measures. The Industry Revolution was underway and a global economy was developing. The need for unified measurement was becoming obvious. There were two choices: the Metric System,  and the British Imperial System. Between 1850 and 1900 the Metric System made rapid progress. It was adopted throughout the Europe, in Latin America, and in many countries elsewhere. It even became a key part of the language of science. There are two clusterings of Metric System in science and engineering: one cluster, based on the Centimeter, the Gram, and the Second, is called the CGS system; the other, based on the Meter, Kilogram, and Second, is called the MKS system

In 1875, most of the leading industrialized countries (including the U.S., but not UK) signed the Treaty of the Meter. The treaty established the International Bureau of Weights and Measures, which we now call the International System of Units (SI).

Since 1875, the metric system has met popular opposition in every country at the time of its adoption. People don't want to change their customary units, which are part of how they see and control the world. This opposition has been largely overcome everywhere.

Most of the US system of measurements is the same as that for the UK. The biggest differences are in Capacity which has both liquid and dry measures, as well as different standards, e.g.  the US liquid gallon is smaller than the UK gallon; there are also measurements known at the US section, township, and others.

Units of Measurement have been associated with the progresses of Science and Technologies, as well as the development of the global economy, they are part of our daily life. 

This Dictionary of Units and the Conversion Calculators of Units are principally designed for school students, to serve as the handy tools for their convenience in learing, studying classes, and understanding the diversity of cultures from different nations. We hope that it could also help parents and professionals for different applications and purposes.


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