Iota (ι) in LaTeX
In LaTeX maths mode, \iota produces the lowercase Greek letter iota (ι). Uppercase Iota is identical to a Latin capital I, so there is no \Iota command; type I.
LaTeX command
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Iota, \iota, is a small dotless letter resembling a Latin i without its dot. It is one of the less common Greek letters in mathematics, but it appears as the symbol for an inclusion or injection map in algebra and category theory, written \iota : , and occasionally as a small index or a decay constant in physics.
The word iota also means a tiny amount, and the letter is sometimes chosen deliberately for a small quantity. In the APL programming language iota is the index generator. Whatever the use, \iota must be inside maths mode, and it renders italic by default like other single-letter variables.
There is no uppercase command because the capital Greek Iota is drawn exactly as a Roman I. If you want an upright roman capital, type \mathrm{I}; a plain I in maths mode is italic. Take care not to confuse \iota with a lowercase Latin i, which carries a dot.
Other forms
\iotalowercase iotaExamples
$\iota$lowercase iota inline
$\iota : H \hookrightarrow G$an inclusion map of a subgroup
$\iota(a) = a$an inclusion acting as the identity on elements
$x_\iota$iota as a subscript index
Tips and common mistakes
- There is no
\Iota; uppercase Greek Iota is a Latin I, so type I, or\mathrm{I}for upright. \iotais dotless; do not confuse it with a Latin i, which has a dot.\iotais maths-mode only; wrap it in .- For the hooked inclusion arrow that often accompanies iota, use
\hookrightarrow.
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Convert your maths to LaTeX →FAQ
Is there a capital iota command in LaTeX?
No. The uppercase Greek Iota looks identical to the Latin capital I, so LaTeX provides no \Iota; simply type I, or \mathrm{I} for an upright shape.
What is iota used for in mathematics?
Most often it denotes an inclusion or injection map, as in \iota : . It can also serve as a small index or a symbol for a tiny quantity.
Does iota have a variant form?
No, there is no standard \variota. Only the single command \iota exists for this letter.