--- loncom/xml/londefdef.pm	2017/01/30 20:14:31	1.456.2.3
+++ loncom/xml/londefdef.pm	2019/05/17 15:41:32	1.456.2.4
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Tags Default Definition Module 
 #
-# $Id: londefdef.pm,v 1.456.2.3 2017/01/30 20:14:31 raeburn Exp $
+# $Id: londefdef.pm,v 1.456.2.4 2019/05/17 15:41:32 raeburn Exp $
 # 
 #
 # Copyright Michigan State University Board of Trustees
@@ -92,6 +92,14 @@ sub start_m {
     my $inside = &Apache::lonxml::get_all_text_unbalanced("/m",$parser);
     if ($target eq 'web' || $target eq 'analyze') {
 	&Apache::lonxml::debug("M is starting with:$inside:");
+        if (!($inside =~ /^\s*\$.*\$\s*$/ || $inside =~ /^\s*\\[([].*\\[)\]]\s*$/)) {
+            # Non-math LaTeX will not be rendered correctly with MathJax
+            # and it should be avoided anyway.
+            # On top of that, MathJax will render math without $, but
+            # it will fail with tth. This is worth a warning.
+            # (even though some people might just use latex for printing)
+            &Apache::lonxml::warning(&mt("Missing \$ in <m>."));
+        }
 	my $eval=&Apache::lonxml::get_param('eval',$parstack,$safeeval);
 	if ($eval eq 'on') {
 	    $inside=&Apache::run::evaluate($inside,$safeeval,$$parstack[-1]);