Transition-
This allows a transition to change speed over its duration.
Its options are:
(1) Ease, this is default, the transition starts slowly, speeds up, and then ends slowly.
(2) Ease-in, the transition starts slowly.
(3) Ease-out, the transition ends slowly.
(4) Ease-in-out, the transition starts slowly and ends slowly.
(5) Linear, the transition maintains the same speed throughout.
For maximum browser support, you should use the following prefixes:
(1) transition-
(2) -webkit