The word sap has two main meanings:

1. A sticky fluid that flows through plants and trees, carrying water and nutrients from the roots to the leaves. In spring, people tap maple trees to collect sap, which they boil down to make maple syrup. It takes about 40 gallons of sap to make just one gallon of syrup! Some trees, like pines, produce a thick, resinous sap that was historically used to waterproof ships and make products like turpentine.
2. To gradually weaken or drain someone's strength or energy. A long hike in the summer heat can sap your energy, leaving you exhausted. Worry can sap your concentration, making it hard to focus on homework. When something saps your strength, it slowly takes away your power or resources, like how tree sap flows out when you tap a maple. You might say that arguing with your sister sapped your patience, or that staying up too late sapped your energy for the next day's soccer game.