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Symbol | Definition |
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≡ | exactly equal |
≈ | approximately equal to |
= | equal to |
digits | indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …) |
Inch of mercury (inHg and "Hg) is a unit of measurement for pressure. It is still used for barometric pressure in weather reports, refrigeration and aviation in the United States.
A centimetre of water (US spelling centimeter of water, abbreviated cm H2O or cm H2O) is a less commonly used unit of pressure derived from pressure head calculations using metrology.