Guide (noun)

1. A person who shows the way to someone by leading or advising them.
2. A book, map, or other information source that provides instructions or information.
3. Something that serves as a model for others to follow.
4. A tool that helps to direct or control the position or movement of something.
5. A device that steadies or regulates the motion of something.

Origin:

Middle english, from old french, from guider to guide; akin to old high german wizzan to show.

Examples:

1. The tour guide showed us around the city.
2. This guidebook will help you plan your trip.
3. She was a guide for young musicians.
4. The carpenter used a guide to make straight cuts.
5. The machine has a guide to keep the material in place.