# Arrow notations “⥊” and “⥋”

I'm wondering what the following arrows are typically used for and what do they signify:

I figured since they are provided by the package MnSymbol as mathematical symbols, this is the right place to ask. If this is not the case, then could you please point me to the comprehensive list of arrows used for mathematical notations, if there is one?

• Could it be a symbol chemists use? masterorganicchemistry.com/2011/02/09/… I've never seen this as mathematical notation, but there are a lot of Unicode characters I could say the same thing about. – Steve Kass Jan 5 '18 at 0:51
• @SteveKass You got me: originally I was searching for the definition of these arrows in the field of chemistry, but it turned out that various sources use these arrows quite offhandedly, sometimes denoting co-dependency of reactants, chemical equilibrium (which is against IUPAC rules), reversibility in general etc., so I'm hoping that mathematicians could share their experience that could help to understand what these arrows are meant to be used for. – andselisk Jan 5 '18 at 1:01
• The best I can suggest is to look at the history of the Unicode block that contains these characters. en.wikipedia.org/wiki/… If they were Unicode characters before they were added to the LaTeX package, that might be helpful. – Steve Kass Jan 5 '18 at 1:21
• @SteveKass Good suggestion, but I saw these arrows in the old books when Unicode wasn't even a thing. I added the corresponding codes only for the unambiguous interpretation of the symbols. – andselisk Jan 5 '18 at 1:46