Leaves are the flat, usually green parts of plants that grow from stems or branches. Most leaves feel smooth or slightly waxy, and they come in countless shapes: some are round, some pointed, some have smooth edges, and others have jagged teeth along their sides. Maple leaves look like open hands, oak leaves have wavy lobes, and pine needles are leaves too, just thin and sharp.

Leaves do essential work for plants. They capture sunlight and use it to make food through a process called photosynthesis. Inside each leaf, a green substance called chlorophyll absorbs light energy and converts carbon dioxide from the air and water from the soil into sugar that feeds the plant. This process also releases oxygen, which is why forests and gardens help keep our air fresh and breathable.

In fall, many trees stop making chlorophyll, and their leaves turn brilliant colors (yellow, orange, red, and brown) before falling to the ground. These fallen leaves create a crunchy carpet in autumn and eventually decompose, enriching the soil.

The word can also mean departing or going away: when your mom leaves for work in the morning, she's heading out the door. And if you leave your math homework at home, you've accidentally left it behind.