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Hear me out here. I tried to do \nless which I found online, however I was just given and undefined control sequence error message. What should I do?

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    You need to load amssymb for \nless.
    – moewe
    Commented Sep 13, 2018 at 11:51
  • Thank you. I was using amsmath and I thought that would be enough. Commented Sep 13, 2018 at 12:07
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    you may find \not \lt gives you what you are looking for
    – Henry
    Commented Sep 13, 2018 at 14:13
  • The title of the question sounds weird. I'd recommend to change it to understand the question more easily. What about: What is the not less than operator in LaTeX?
    – Charlie
    Commented Sep 18, 2018 at 16:43
  • When I come across a macro that is undefined, I often just come to this site and use the search feature on the macro name. If you can find a question or answer here where it is used, the MWE will always point you towards which package to load. Commented Sep 18, 2018 at 17:46

2 Answers 2

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Go to Detexify and draw what you want:

enter image description here

  1. the symbol is \nless
  2. you need \usepackage{amssymb}
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    Note that some fonts and their supporting .sty files already include the \nless symbol without having to load amssymb. Among these are Lucida Bright (\usepackage{lucidabr}) and MathTime Pro 2 (\usepackage{mtpro2}).
    – murray
    Commented Aug 4, 2019 at 19:16
  • Is there a use case where this would be preferable to the "greater or equal" sign ?
    – Sileo
    Commented Dec 25, 2020 at 20:48
  • @Rphad ? (I don't understand your comment)
    – Rmano
    Commented Dec 25, 2020 at 21:52
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    @Rphad @Rmano It is also a matter of context: If I am checking if a<b and my test say it is not, I would prefer to indicate it with this \nless (thinking about statistical tests).
    – Luis
    Commented Jan 11, 2021 at 17:22
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    If we're working in a partial order that is not a linear order, then it's possible for $x \nless y$ to be true but $x \geq y$ to be false. For example, if we are dealing with functions $\mathbb{R} \rightarrow \mathbb{R}$ ordered pointwise, then $f \nless g$ is true iff there is some $x$ such that $f(x) \geq g(x)$; $f \geq g$ is true iff for every $x$ we have $f(x) \geq g(x)$. Commented Dec 11, 2023 at 16:01
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A more general response was provided by henry:

"you may find \not \lt gives you what you are looking for"

This works for users of Jupyter and MathJax who may not be able to load libraries. $\not \lt$

Otherwise, you can go with Rmano's recommendation above, which is to look in Detexify and end up loading the amssymb library.

"not less than" symbol in MathJax on Jupyter

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  • Welcome! Unfortunately, MathJax etc. are not TeX-based and off-topic for this site.
    – cfr
    Commented Apr 10 at 1:25
  • Also, please don't post images of code. Code should be posted as text and formatted appropriately, preferably in the form of a complete minimal example.
    – cfr
    Commented Apr 10 at 1:32
  • No LaTeX package that I know of defines \lt or \gt for < and >. They're used in MathJax (which isn't LaTeX) in order to overcome limitations of JavaScript.
    – egreg
    Commented Apr 10 at 13:18

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