For what reason, cause, or purpose.

• Introducing a direct question.
• With a negative, used rhetorically to make a suggestion.

The reason or explanation.

• The cause or purpose for something.

Exclamation of mild surprise, indignation, or impatience.

To ask someone why.

The name of the Latin letter Y or y.

• A Y-shaped object or junction, especially of road or railroad.

To form something into a Y shape.

• To reverse a train using a wye/triangle.