He fell unconscious after the accident.

Never underestimate the power of determination.

She is an undergraduate student at the university.

The subway is an underground transportation system.

The subway is an underground transportation system.

The hiker's excoriation of the tree bark revealed the beautiful patterns underneath.

The divers explored the undersea cave.

The instructions were clear and understandable.

She has a deep understanding of the subject.

My employer is very supportive and understanding.