Difference between two inequality symbols I have come across the symbol $ \leqq$ in a paper I am reading. Is there any difference between this symbol and the symbol $ \leq $?
No, they are the same. You should consider them the same symbol in different 'fonts' rather than two different symbols.
Y ≦ X

Means Y is than or equal to every value of X for each correspending component in vector inequality.

Difference is that ≤ is used in calculus and ≦ in vector analysis.

Also see http://en.wikipedia.org/wiki/List_of_mathematical_symbols