Trefoil
Part of speech: noun
Definition: Any of several plants of the pea family, having compound, trifoliate leaves; especially one of the genus Trifolium. A symbol having the shape of such leaves, especially when used as an architectural ornament.
Clover
Part of speech: noun
Definition: A plant of the genus Trifolium with leaves usually divided into three (rarely four) leaflets and with white or red flowers.
Example sentence: To make a prairie it takes a clover and one bee, One clover, and a bee, And revery. The revery alone will do, If bees are few.