Leaf Margins 

	To the left is a leaf with no features along its margins at all.  This would be defined as entire.  To the right is a leaf slightly serrate because the teeth are sharp and point upward.
	This is the leaf of american chestnut, Castanea dentata.  The leaf sometimes has dentate margins where the teeth point out perpendicular to the midrib.  Very often the leaf is more serrate than it is dentate.
	This pic better shows the typical serrate leaf margin.  The "teeth" here are "sharp" enough, and they do point upward.
	Crenate margins are rounded.  The example here is of a common local species Glechoma hederacea - ground ivy.