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[Quantities, their Symbols, Units of Measure and Definitions](https://content.leybold.com/migration/en/knowledge/quantities-their-symbols-units-of-measure-and-definitions) # Quantities, their Symbols, Units of Measure and Definitions ## Basic Terms and Concepts in Vacuum Technology - [What is the definition of Volume?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-volume) - [What is the definition of Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-pressure) - [What is the definition of Total Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-total-pressure) - [What is the definition of Saturation Vapor Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-saturation-vapor-pressure) - [What is the definition of Vapor Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-vapor-pressure) - [What is the definition of Standard Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-standard-pressure) - [What is the definition of Ultimate Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-ultimate-pressure) - [What is the definition of Ambient Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-ambient-pressure) - [What is the definition of Overpressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of) - [What is the definition of Working Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-working-pressure) - [What is the definition of Particle Number Density?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-particle-number-density) - [What is The Ideal Gas Law?](https://content.leybold.com/migration/en/knowledge/what-is-the) - [What is the definition of Gas Density?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-gas-density) - [What is the definition of Absolute Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-absolute-pressure) - [What is the definition of Partial Pressure?](https://content.leybold.com/migration/en/knowledge/what-is-the-definition-of-partial-pressure) See less ▼ - [Vacuum Physics](https://content.leybold.com/migration/en/knowledge/vacuum-physics#main-content) - [Basic terms and concepts in vacuum technology](https://content.leybold.com/migration/en/knowledge/vacuum-physics#basic-terms-and-concepts-in-vacuum-technology) - [Atmospheric Air](https://content.leybold.com/migration/en/knowledge/vacuum-physics#atmospheric-air) - [Gas laws and models](https://content.leybold.com/migration/en/knowledge/vacuum-physics#gas-laws-and-models) - [Kinetic Gas Theory](https://content.leybold.com/migration/en/knowledge/vacuum-physics#kinetic-gas-theory) - [Types of flow and conductance](https://content.leybold.com/migration/en/knowledge/vacuum-physics#types-of-flow-and-conductance) - [Vacuum Generation](https://content.leybold.com/migration/en/knowledge/vacuum-generation#main-content) - [Vacuum pumps: A survey](https://content.leybold.com/migration/en/knowledge/vacuum-generation#vacuum-pumps-a-survey) - [Oscillation displacement vacuum pumps](https://content.leybold.com/migration/en/knowledge/vacuum-generation#oscillation-displacement-vacuum-pumps) - [Liquid Sealed Rotary Displacement Pumps](https://content.leybold.com/migration/en/knowledge/vacuum-generation#liquid-sealed-rotary-displacement-pumps) - [Analysis of gas at low pressures using mass spectrometry](https://content.leybold.com/migration/en/knowledge/analysis-of-gas-at-low-pressures-using-mass-spectrometry#main-content) - [The quadrupole mass spectrometer (TRANSPECTOR)](https://content.leybold.com/migration/en/knowledge/analysis-of-gas-at-low-pressures-using-mass-spectrometry#the-quadrupole-mass-spectrometer-transpector) - [Instructions for vacuum equipment operation](https://content.leybold.com/migration/en/knowledge/instructions-for-vacuum-equipment-operation) - [Quantities, their Symbols, Units of Measure and Definitions](https://content.leybold.com/migration/en/knowledge/quantities-their-symbols-units-of-measure-and-definitions#main-content) - [Basic Terms and Concepts in Vacuum Technology](https://content.leybold.com/migration/en/knowledge/quantities-their-symbols-units-of-measure-and-definitions#basic-terms-and-concepts-in-vacuum-technology) - [Default HubSpot Blog](http://blog.leybold.com/) [![Chill listening crop-3](https://content.leybold.com/hs-fs/hubfs/logo.png?width=24&height=24&name=logo.png "Chill listening crop-3")](https://www.leyboldproducts.com) www.leybold.com Knowledge Center Copyright © 2026, Leybold USA Inc