Graph :

A function is odd function if the graph of the function is symmetric about the origin.

Observe the graph.

The graph  is odd function, because it is symmetric about the origin. \ \

Graph : \ \

A function is even function if the graph of the function is symmetric about the axis.

Observe the graph.

The graph  is even function, because it is symmetric about the axis. \ \

The function on one side of the graph is reflects on other side. \ \

\ \

  is odd function. \ \

is even function.