Subscripts

I cant get subscripts to function properly. I want a subscript number immediately after a word, but the syntax seems to require a space before the << - opening of the expression. So the expression
word<<$_2$>> that in ordinary LaTex would place the number as subscript immediatly after ‘word’ gives an error message. The expression word <<$_2$>> gives a subscript number, but then with a space between the word and the number.
Any solution or workaround?