What tex symbol is used for the "let" word?

Question

Years ago I attended lectures where the lecturer used a "let" quantifier. The symbol was very handy, and now I wish to type it in TeX. The problem is that I fail to type it or even guess its name. What tex symbol is used for the "let" word? And what other names does it have, if any?

For now, at https://detexify.kirelabs.org/classify.html (the site, suggested in my similar question about another symbol) the best symbol I found is \sqsupset - is it OK in TeX to use glyphs with wrong semantic?

I've attached an image

Answer 1

Disclaimer: Neither I nor other users who commented on your question have never seen the symbol used for this meaning; we can hence fairly denote this usage as rather uncommon, to say the least. If you are writing your document for other people to read, you'll probably confuse them.

This being said, if the typeset document is supposed to be read by

1. yourself only, or
2. a restricted circle of people sharing a love for uncommon notation, or simply
3. people you don't like too much :-)

then the LaTeX way to use it is to define a semantic command, e.g.

\documentclass{article}
\usepackage{amsmath,amssymb}
\newcommand*{\Let}{{\sqsupset}}
\begin{document}
$\Let \sqrt{2}\in\mathbb{Q} \implies \exists \, n,d : \frac{n}{d} = \sqrt{2}$
\end{document}

Note the extra pair of braces around \sqsupset: by default it has \mathrel spacing, which isn't appropriate here, and the braces around it turn it into a \mathord.

IMO you shouldn't do it and just write a proper sentence...