italic after math equation: how to solve (not solved with $) [duplicate] This question already has an answer here: I am not an expert with equations on latex. I have wrote these ones within a chapter of a book, but I missed how to write the label on the left with the equation number. Moreover, the text after the equations is italic for a couples of lines and I did not find the way to fix it. What is wrong? (Edit with suggestions proposed) \documentclass[a4paper,11pt, twoside, openright]{book} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english]{babel} \usepackage[a4paper,top=3.5cm,bottom=3cm,left=3cm,right=3cm]{geometry} \usepackage{fancyhdr} \usepackage{setspace} \usepackage{graphicx} \usepackage{caption} \captionsetup{font=small} \usepackage{topfront} \usepackage{emptypage} \usepackage{natbib, authoryear} \graphicspath{figure} \usepackage{longtable} \usepackage{chngcntr} \usepackage{rotating} \usepackage{mathtools} \usepackage{textgreek} \usepackage{hyperref} \begin{document} yi \in Y_{i} \sim mathrm{Multinom}(\pi^1_i , \pi^2_i , \pi^3_i ) \pi^k_i = \frac{exp(\eta^k_i)} {1+ \exp(\eta^2i) + exp(\eta^3i)}\hfill k= 1,...,3 \eta^k_i = ln(\frac{\pi^k_i }{\pi^1_i}) = \beta^k_0 + x_i_1\beta^k_1 + \sum^11_{j_=_3 } x_i_j\beta^k_j \hfill k= 2,3 \eta^1_i = 0 some text which is italic \end{document} i have not solved the issue substituing with$\pi$marked as duplicate by Werner equations StackExchange.ready(function() { if (StackExchange.options.isMobile) return;$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var $hover =$(this).addClass('hover-bound'), $msg =$hover.siblings('.dupe-hammer-message'); $hover.hover( function() {$hover.showInfoMessage('', { messageElement: $msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Oct 23 '18 at 17:52 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. • if you get a tex error then you should ask about the error message (the pdf output after any error isn't designed for use,it may possibly be useful for debugging but nothing else) – David Carlisle Oct 23 '18 at 17:37 • You need to start the math mode with (for example) $and end it with$ (and remove the \bigskip) also exp should be \exp and Multinom should be \mathrm{Multinom} – David Carlisle Oct 23 '18 at 17:39 • @DavidCarlisle you mean i have to add [ and ] for each line or just once at the beginning and at the end of the equations?thank you – ggg Oct 23 '18 at 17:40 • really you should start with a basic tutorial on latex, as there are so many errors here in so few lines... I'll post something as an answer too long for a comment. – David Carlisle Oct 23 '18 at 17:41 • @DavidCarlisle thank you, i read a lot about equations but still i was not able to solve the problem – ggg Oct 23 '18 at 17:42 1 Answer I had to take some guesses as to the intended meaning in some cases... \documentclass[a4paper,11pt, twoside, openright]{book} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage{mathtools} \DeclareMathOperator\Multinom{Multinom} \begin{document} some text \begin{equation} yi \in Y_{i} \sim \Multinom(\pi^1_i , \pi^2_i , \pi^3_i ) \end{equation} some more text${x_i}_1$??$\sum^1\$ ???
\begin{align}
\pi^k_i &= \frac{\exp(\eta^k_i)} {1+ \exp(\eta^2i) + \exp(\eta^3i)}  &&  k= 1,\dots,3\\
\eta^k_i &= \ln(\frac{\pi^k_i }{\pi^1_i}) = \beta^k_0 + x_{i1}\beta^k_1 +    \sum^11_{j=3 } x_{ij}\beta^k_j &&k= 2,3\\
\eta^1_i &= 0
\end{align}

some text which is italic
\end{document}
• Thank you very much. This solved all the issues but not the one of italic. could it be because i'm using texshop on a mac? just a couple of questions: there is a way to left align the first equation? and can i used just one numbered label for all this lines (instead of a number for each line)? – ggg Oct 23 '18 at 18:12
• @ggg you can left align everything by using fleqn option on \documentclass and you can replace align by \begin{equation}\begin{aligned}...\end{aligned}\end{equation} if you want a single number. If you need more help then ask a new question not comments under an existing answer, but please take some time to read the amsmath user guile (amsldoc.pdf) first, there are many examples of all these things. – David Carlisle Oct 23 '18 at 18:16