A can of paint is to a paintbrush as a spool of thread is to a sewing needle. This is a relationship of function. Both show the tool needed to perform a task.

A shirt is to a button as a belt is to a belt buckle. A button is used to close a shirt; a belt buckle is used to close a belt.

Camera is to photograph as teakettle is to a cup of tea. The camera is used to make the photo; the teakettle is used to make the tea.

A trapeze performer is to a clown as swings are to a sliding board. This relationship shows a classification. Trapeze performers and clowns are found at circuses; swings and sliding boards are found on playgrounds.

Leather boots are to cow as pearl necklace is to oyster. The leather to make the boots comes from a cow; the pearls to make the necklace come from oysters.