What are scleronomous and Rheonomous constraint?

scleronomous constraint:
constraint that is independent of time. e.g. pendulum of inextensible string. x² + y² = l² equation is independent of time.
Rheonomous constraint:
constraint that contains time explicity. e.g. pendulum of inextensible string. x² + y² = l²(t). where l(t) is the length at time (t).