Leaves can be classified as either simple or compound. Simple leaves have a single blade. Although undivided into separate leaflets, the blade of a simple leaf may be lobed with deep sinuses.

      Compound leaves are separated into two or more leaflets. Compound, or dissected leaves, are further classified as pinnate or palmate. Pinnately compound leaves are dissected very much like a feather, with leaflets located on both sides of a main axis called a rachis. Palmately compound leaves have leaflets that share a common insertion point at the end of the petiole. Both pinnately and palmately compound leaves can be divided again resulting in bipinnate or bipalmate leaf forms.

      Differential growth within a developing leaf primordium determines the shape of the mature leaf. Initially, growth is continuous along the margin of a leaf primordium. After the leaf primordium becomes differentiated into a leaf blade and leaf base region, differential growth may occur along the primordial blade margin. If growth is more or less continuous along the margin, the primordium will develop into a simple leaf. If growth is localized along the margin, the discrete areas of growth may develop into the separate leaflets of a compound leaf. All manner of intermediates can be found between leaves with a simple lamina and those with a dissected blade. Many simple leaf forms initiate what appear to be primordial pinnae or leaflets, but these develop into lobes or teeth because of continued growth between the initially separate areas of growth along the primordial margin.

      Most palms have compound leaves that develop in a completely different way than described in the previous paragraph. Palm leaves start out as primoria with continuous growth along their margins. The palm leaf becomes separated into separate leaflets by the physical breakdown and tearing of tissues within the initially simple primordial leaf blade. The breakage into separate leaflets occurs as the blade expands and grows out of the bud. Strips of unbroken tissue, called reins, may remain connecting the ends of the leaflets in both feather (pinnately compound) or fan (palmately compound) palm leaves.

      Leaves of some plants, such as Monstera and Philodendron, in the family Araceae, have holes in them. These holes occur late during expansion due to apoptosis (programmed cell death) in those regions of the blade.

      Some monocots (especially grasses and sedges) differ from typical dicots because their leaves retain basal intercalary meristems. This meristem, located near the base of the leaf, continues to produce new cells even in an otherwise fully mature leaf. As expansion occurs, the oldest cells are found near the tip of the leaf and the newest cells are located near the leaf base. This basal meristem explains why we can continually cut our lawns and the grass keeps growing back.

      Some plants develop unifacial or equifacial leaves that apparently lack adaxial and abaxial surfaces. Instead of being flattened, the leaf blade is terete (cylindrical). In some plants such as Musa (banana), only the very tip of the leaf is unifacial and in others such as Sanseveria cylindrica, the entire leaf is unifacial.

      Peltate leaves have umbrella-shaped blades with a petiole that is attached in the middle of the abaxial surface.