Pine has two main meanings:

1. An evergreen tree with needle-like leaves and woody cones. Pine trees stay green all year round and often grow tall and straight, making them valuable for lumber. Their wood is soft and easy to work with, so builders use it for furniture, floors, and construction. Pine forests cover huge areas in northern climates and mountainous regions. The sticky sap, called resin, smells sharp and fresh. Different species include white pine, yellow pine, and ponderosa pine.
2. To feel a deep longing or sadness for something or someone you can't have. When you pine for something, you don't just want it casually: you ache for it. A homesick camper might pine for their family during a long trip away. Someone might pine for the carefree days of summer vacation once school starts again. The word suggests a kind of gentle, melancholy yearning that doesn't go away quickly. You might hear someone say they're pining away, which means the longing is so strong it's affecting how they feel day to day.