# Name for number of elements of order (1 or) 2 in an abelian group

Let $G$ be an (additive) abelian group. Is there a concise, standard term for the order of the kernel $K$ of the endomorphism $g\mapsto 2g$? Or alternatively, for the index of $K$?

-
Order of 2-torsion of G. –  Georges Elencwajg Mar 15 '10 at 13:30
Thanks! Now I need to type some more because the software won't let me post a comment as short as "Thanks!" –  Mark Meckes Mar 15 '10 at 14:04
Really ? –  Mariano Suárez-Alvarez Mar 15 '10 at 14:15
Well I think for the good of all Math Overflowers, I should post the trick: Simply add the number of spaces you need to reach the limit followed by a punctuation mark. The extra spaces will not be displayed. –  Steven Gubkin Mar 15 '10 at 15:27
You can put in something like "Text$~~~~~~~~\$\{\}\" to avoid the space in front of the punctuation. –  Douglas Zare Mar 15 '10 at 23:34