on

Positioned physically supported by or resting upon a surface or object.

"The book is on the shelf."

Indicating a specific day or date when an event occurs.

"We meet on Monday mornings."

Operating or functioning; switched to an active state.

"Is the television on?"

Continuing forward in a process, activity, or movement.

"Keep on walking until you see it."

In a particular state, condition, or process.

"She is on holiday next week."