A simple leaf blade is undivided as shown on the left (though the margins may be toothed or even lobed). The blade of a compound leaf is divided into several leaflets as shown on the right.

If there is doubt as to whether you are looking at a leaf or a leaflet, locate the lateral buds. Each leaf, whether simple or compound, has a bud at its base (on the twig). There are no buds at the base of each leaflet. In the diagram at the left we would expect a bud at the base of each petiole, but no bud at the base of eatch leaflet of the compound leaf (see diagram below).