What "leaf" means in gardening

A leaf is an above-ground plant organ that is typically flat, thin, and green, with a blade and a petiole or stem that attaches it to the plant stem. Leaves are responsible for photosynthesis, the process by which plants convert sunlight into energy, and they also play a role in transpiration, or the release of water vapor from the plant into the air. Leaves come in a variety of shapes and sizes, and can be either deciduous (falling off in the autumn) or evergreen (remaining on the plant year-round).