1. a railway system that uses a single rail, usually high above the ground
2. to travel around an area in order to find out about it
3. the basic idea that a plan or system is based on
4. something that is extremely important
5. the vehicles moving along a road or street


1. a disease that causes death and spreads quickly to a large number of people
2. a structure from which water is pushed up into the air, used for example as decoration in a garden or park
3. the height of an object or place above sea level
4. an ancient animal or plant (or its shape) that has been preserved in rock
5. able to think in a normal and reasonable way