'skinname-modern' => '{{optional}}',
# Math options
-'mw_math_png' => 'In user preferences.',
-'mw_math_simple' => 'In [[Special:Preferences|user preferences]].',
-'mw_math_html' => 'In user preferences.',
-'mw_math_source' => 'In user preferences (math)',
-'mw_math_modern' => 'In user preferences (math)',
-'mw_math_mathml' => 'In user preferences.',
+'mw_math_png' => 'In user preferences. All mw_math_* messages MUST be different, things will break otherwise!',
+'mw_math_simple' => 'In [[Special:Preferences|user preferences]]. All mw_math_* messages MUST be different, things will break otherwise!',
+'mw_math_html' => 'In user preferences. All mw_math_* messages MUST be different, things will break otherwise!',
+'mw_math_source' => 'In user preferences (math). All mw_math_* messages MUST be different, things will break otherwise!',
+'mw_math_modern' => 'In user preferences (math). All mw_math_* messages MUST be different, things will break otherwise!',
+'mw_math_mathml' => 'In user preferences. All mw_math_* messages MUST be different, things will break otherwise!',
# Math errors
'math_syntax_error' => '{{Identical|Syntax error}}',