Leaves are the principal lateral appendage of the vascular plant stem. They are usually born above the ground and help the plants to perform photosynthesis. The leaves, flowers, fruits, and stems together form the shoot system. Usually, leaves are flattened and have separated upper and lower surfaces which differ in color. The number of stomata in a leaf varies from leaf to leaf, and the amount and structure of epicuticular tissue are different in different leaves.

Leaves are generally green in color because of the presence of a green substance called chlorophyll in them. This substance is also essential at the time of the photosynthesis process that takes place in leaves. A leaf having light-colored or white patches on its edges is called variegated leaves.

Leaves have different sizes, shapes, and textures. Based on these features, they are further classified into many types. Based on the divisions of blades, leaves are divided into simple leaves and compound leaves. A simple leaf is one with an undivided blade while a compound leaf has a fully subdivided leaf. A simple leaf may be dismembered from its lobes, but the gaps between those lobes do not touch the main verb. In a compound leaf, each leaflet is separated along a main or a secondary vein.

The leaves of perennial plants are shed annually and are known as deciduous leaves, while the leaves that remain through winter are known as evergreen leaves. Leaves that are attached to stems by stalks are called petiolate. When they are attached directly without the help of stalks, then they are called sessile. Dicot leaves have blades in such a way that the major veins diverge from one large mid-vein and have smaller combining networks between them. Monocot leaves have narrow blades and are more common in temperate regions.