Elements

The Elements are one of the most basic features of the Inazuma Eleven universe. They can be attributed to most characters and Hissatsu Techniques.

Wind
Wind is weak against Wood and is strong against Earth. Wind element includes other elements such as Water, Ice, lightning and Wind itself.

Earth
Earth is weak against Wind and is strong against Fire. Earth element includes other elements such as Light and Earth itself.

Fire
Fire is weak against Earth and is strong against Wood. Fire element usually only includes Fire itself, although some techniques with the Fire element can be mistaken as a Wood attribute.

Wood
Wood is weak against Fire and is strong against Wind. Wood element includes other elements such as Music, Energy, Space, Darkness and Wood itself. Most wood users have a different range of hissatsu techniques with different elements.

Dark
http://images2.wikia.nocookie.net/__cb20120303205713/inazuma-eleven/images/e/e9/Icon_Dark.png From the looks of things, Dark isn't weak or strong to any of the other 4 elements. It was first shown in Inazuma Eleven Strikers 2012 XTreme where 4 moves are all Dark element. It is known now that all Dark element moves are all used by Team Zero. It only appeared in the GO series so far