# Greek \chi's subscript expressions: how to make it smaller or offset lower?

I am unsatisfied with the way subscript is rendered for the Greek letter \chi. This particular letter is rendered with a small downward offset. I occasionally have to prefix the subscript with \sciptscriptstyle such that, in effect, an expression may look like

\sup{\chi_{\scriptscriptstyle A_n}(x)}[n]


where

\RenewDocumentCommand{\sup}{m O{}}{
\operatorname{sup}\ifstrempty{#2}{}{\limits_{\mathclap{\substack{\expandafter{\scriptscriptstyle{#2}}}}}}
\expandafter{#1}
}


(I admit this snippet is a little messy, especially due to the uncanonical declaration of the optional argument as O{} and testing via \ifstrempty instead of o for the argument type and IfNoValueTF--using the xparse package. I am not entirely clear yet about what syntax is more straightforward.)

Is there a way to redefine \chi keeping the syntax in line with all semantically equivalent concepts, i.e., letters, but having only \chi's subscript expressions smaller or slightly lower? To clarify, I am thinking of redefining the subscript operator _ for \chi only. But I naively suppose TeX' grammar would not let me do that.

An evident work-around would involve defining a new macro using a different syntax like

\newcommand{\Chi}[1]{\chi_{\scriptscriptstyle{#1}}}


So effectively, what I want is just

\chi_{expr}


where expr is rendered smaller or offset lower than default.

• Alternately, you could render \chi a slight distance vertically higher (all the time, not just with subscripts). While messing with a designer's fonts is not ideal, the alternative you propose of setting different size subscripts at the same nesting level could be very confusing. – Steven B. Segletes Jul 15 '14 at 11:06
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