# Making underscore persistent in LaTeX math mode (for long subscripts) [duplicate]

Is there at all a way to make underscores and carets persistent in LaTeX math mode? What I mean, is to be able to write several-character sub/superscripts without using curly brackets. Could LaTeX maybe understand that a white space determines the end of my sub/superscript?

A quick example. I'd like to have something like

x_ij y_ij


Compile to the same result as

x_{ij}y_{ij}


I understand that this is probably not a really reliable thing, but I'm looking to take notes faster during class!

Many thanks

## migrated from stackoverflow.comSep 20 '16 at 18:12

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• No, it's not reliable. You're very likely to forget a space when typing something like Let $x_i$ be the least... which would lead to a long string of weird errors. It would be easier something like x_ij_ so the subscript is delimited by another _ – egreg Sep 20 '16 at 18:17
• Related, if not equal: tex.stackexchange.com/q/96080/21930. – Manuel Sep 20 '16 at 19:40
