International System of Units
Last revised by Daniel J Bell on 3 Nov 2021
Citation, DOI, disclosures and article data
Citation:
Bell D, Vlietstra M, Murphy A, et al. International System of Units. Reference article, Radiopaedia.org (Accessed on 28 Mar 2024) https://doi.org/10.53347/rID-58659
Permalink:
rID:
58659
Article created:
27 Feb 2018,
Daniel J Bell ◉
Disclosures:
At the time the article was created Daniel J Bell had no recorded disclosures.
View Daniel J Bell's current disclosures
Last revised:
3 Nov 2021,
Daniel J Bell ◉
Disclosures:
At the time the article was last revised Daniel J Bell had no recorded disclosures.
View Daniel J Bell's current disclosures
Revisions:
14 times, by
5 contributors -
see full revision history and disclosures
Sections:
Tags:
Synonyms:
- SI units
- Système international d'unités
- International Unit System
- Systeme international d'unites (SI units)
- SI base units
- SI derived units
- Derived SI unit
- Derived SI units
The International System of Units, or the SI units (shortened from the French Système international d'unités) is the globally-adopted system of units of measurement. It is the modern iteration of the metric system. It superseded all prior systems including CGS and MKS, although in certain fields, including radiation physics, some legacy units linger, especially in the USA, e.g. rad.
Seven base units are defined:
- second (s) (time)
- meter (m) (distance)
- kilogram (kg) (mass)
- ampere (A) (current)
- kelvin (K) (temperature)
- mole (mol) (amount of substance)
- candela (cd) (luminous intensity)
All other units can be derived from these base units and are known as the derived SI units, e.g. hertz.
See also
Quiz questions
{"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":58659,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/international-system-of-units-1/questions/2789?lang=us"}
References
- 1. François Cardarelli. Encyclopaedia of Scientific Units, Weights and Measures. (2012) ISBN: 9781447111221
- 2. The International System of Units (SI) 9th edition (2019) International Bureau of Weights and Measures (BIPM) read online
Incoming Links
Articles:
- Radioactivity units
- Coherent system of units
- Medical abbreviations and acronyms (K)
- Henry (SI unit)
- Blood pressure
- Ionisation chamber
- Weber (SI unit)
- Medical abbreviations and acronyms (S)
- Medical abbreviations and acronyms (L)
- Numbers, units and operators
- Maxwell (CGS unit)
- CGS system
- Medical abbreviations and acronyms (A)
- Becquerel (SI unit)
- Kerma
- Magnetism
- Gyromagnetic ratio
- Exposure
- MKS system
- Medical abbreviations and acronyms (G)
Multiple choice questions:
Related articles: Imaging physics
- imaging physics
- imaging in practice
- imaging technology
-
x-ray physics
- ionizing radiation
- interaction with matter
- x-ray spectrum
- radiation units
- effective dose
- entrance skin dose
- radiation safety
- radiation damage (biomolecular)
- radiation damage (skin injury)
- stochastic effect
- CT physics
-
MRI physics
- B0
- chemical shift
- dependence of magnetization (proton density, field strength and temperature)
- echo time
- eddy currents
- electromagnetic induction
- Ernst angle
- flip angle
- Larmor frequency
- magnetic dipole
- magnetic field gradient
- magnetic susceptibility
- magnetism
- molecular tumbling rate effects on T1 and T2
- net magnetization vector (NMV)
- relaxation
- repetition time
- resonance and radiofrequency (RF)
- units of magnetism
- ultrasound physics
- nuclear medicine physics