Here are some examples:
* The judge was lenient on the young offender, giving him probation instead of jail time.
* My parents were lenient about my curfew when I was a teenager.
* The teacher is known for being lenient with her grading.
Leniency can also refer to the act of being lenient, or the quality of being lenient.
In general, "lenient" implies a more relaxed and understanding approach, often used in situations where someone could be treated more harshly.