# Using iota subscripts in math mode

Is there a way to apply iota subscripts to arbitrary alphabets in math mode ?

An example is ῳ.

• As in ᾳ ? Not really, not out of the box, what purpose do you have in mind? I mean, I'm sure you could make it happen but why? Mar 14 '17 at 3:01
• Yes, I have some purposes and just curious to see if the iota subscripts can be applied in math mode. Mar 14 '17 at 3:03
• What's an iota subscript? @Au101 ?
– cfr
Mar 14 '17 at 3:10
• @cfr The iota is the greek letter ι, it's the Greek i. In Ancient Greek (not sure about Modern) it can form a sort of compound with the letters α η and ω where a small version is placed underneath: ᾳ ῃ ῳ. This is known as the iota subscript. These are read as diphthongs with the first vowel long: en.wikipedia.org/wiki/Iota_subscript Mar 14 '17 at 3:14
• ῳ is equivalent to ωι, which can be considered as an abbreviation for the latter form. The ι sound was originally pronounced but was lost later so the form ῳ was introduced to capture the original etymology perhaps. (see en.wikipedia.org/wiki/Iota_subscript for details) Mar 14 '17 at 3:29

You can basically use anything as a centered subscript:

\documentclass{article}
\usepackage[LGR,T1]{fontenc}
\usepackage{amsmath}

\usefont{LGR}{cmr}{m}{n}\symbol{"7C}%
}}

\DeclareRobustCommand{\ai}[1]{{\mathpalette\doai{#1}}}
\newcommand{\doai}[2]{%
\oalign{%
$#1#2$\cr
\hidewidth$#1\text{\adscriptiota}$\hidewidth\cr
}%
}

\begin{document}

$\ai{\alpha}\ai{b}\ai{\gamma}$

\end{document}


If you want special positioning under particular letters, you have to do it by hand. The case of letters with descenders is tough, as exemplified by \gamma.

• Thanks a lot! Is the syntax \usefont{LGR}{cmr}{m}{n}\symbol{"7C} determine the form of the iota subscript here ? Mar 14 '17 at 7:59
• @Johannes Yes, you can use other font families instead of cmr, provided they have support for LGR. Mar 14 '17 at 8:03
• Sorry, I was not sure about the mechanism of displaying a image here. I was wondering it might be better to not use the letter b here but a more challenging one such as g here to show the position of iota subscripts. Mar 14 '17 at 10:11
• @Johannes I'll do it. Mar 14 '17 at 10:16