Math 2.0

Concept

Sqb2:

Summary

Degree of a field extension: if FF is an extension of a field EE, then [F:E][F:E] denotes the degree of the field extension F/EF/E. For example, [ℂ:ℝ]=2[\mathbb C:\mathbb R]=2.

Index of a subgroup: if HH is a subgroup of a group EE, then [G:H][G:H] denotes the index of HH in GG. The notation ∣G:H∣\lvert G:H\rvert is also used.

Further reading

  1. Wikipedia, page 73634, revision 1376316324, Glossary of mathematical symbols, section Brackets > Square brackets. adopted
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Changed4 November 2026

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