Bar and Mbar
The Bar is an engineering unit defined as 1Bar=100,000 Pa. Also commonly used is the millibar (symbol mbar).
1mbar = 0.001 bar = 100 Pa = 1 hPa.
The millibar is often used to denote atmospheric pressure, and the units of pressure can be either "hPa" or "mbar", which are exactly equal.
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