# Omega (Greek letter)

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Omega (uppercase Ω, lowercase ω) is the 24th and last letter of the Greek alphabet.[1] In the Greek numeric system, it has a value of 800. Pronounced [ɔ:] or 'aw' as in 'raw'.[2][3]

## Symbol uppercase Ω

Astronomy

• Density of the universe, also referred to as the cosmological density parameter. with components of mass density, ΩM, and vacuum energy density, ΩL.[4][5][6]

Chemistry

• Designation for the last carbon on the chain in a fatty acid

Electricity

• Ohm: SI unit of electrical resistance
• Siemens (unit), abbreviated S, is the reciprocal of the ohm.

Mathematics

• Omega constant (Lambert’s W function)[7]
• Chaitin’s constant: the probability that a randomly selected valid program string is interpreted by a halting

term[8]

• Calculus: a 2-D region
• A theoretical measure of the execution of an algorithm, (e.g. required time or memory) given the problem size n (e.g. the number of items).[9]
• Stochastic process[10]

Meteorology

• Used to designate vertical motion in the atmosphere[11]

Statistics

• Sample space
• Set of possible outcomes

Literary

• End or last thing in a series[12]

Physics

• Solid angle or rate of precession in a gyroscope[13]
• Omega baryons (particle physics)
• Negatively charged elementary particle with a mass 3270 times the mass of an electron.[14]
• Omega minus b: a very short-lived unstable meson with mass 1532 times the mass of an electron (aka omega meson)[15]

## Symbol lowercase ω

Mathematics

• The set of all natural numbers[16]

Physics

• Angular frequency

## References

1. Greek Omniglot
2. Omega pronunciation Ancient Greek tutorials, UC Berkeley
3. [1] Meteorite Book, Northern Arizona University
4. Curvature Astrophysics
5. Cosmological curvature Cosmology
6. [2] Wolfram Math World
7. [3] School of Computer Sciences, Carnegie Mellon University
8. [4] National Institute of Standards and Technology
9. Formal definition and basic properties Stochastic process
10. [5] JetStream – Online school for weather, National Weather Service
11. [6] Ask Oxford
12. [7]Wolfram Math World
13. [8] Merriam Webster Online
14. [9] Merriam Webster Online
15. Notation Natural number