Ponder (verb)

1. To think about something carefully, often for a long time.
2. To consider something deeply and at length.

Origin:

From middle english pondren, from old english pondrian ("to weigh, consider"), from proto-germanic *pundrōną ("to weigh"), from proto-indo-european *pénd- ("to weigh, stretch out").

Examples:

1. He was pondering his next move.
2. She was pondering the problem for hours.
3. He was pondering over the decision he had to make.
4. The question made her ponder for a moment.
5. He spent the evening pondering the meaning of life.