is an adjective meaning passionate and intense, or all-consuming. (A second definition could be burning, glowing, or intensely hot).
Fervent is also an adjective, meaning enthusiastic or excited.
Here are some example sentences:
During presidential debates, candidates hurl fervid accusations at each other while defending their positions on the issues.
Vacationers enjoy relaxing in the hot springs, with some claiming the fervid water has healing powers.
His fervent energy upon winning a trip to Italy made it impossible for him to sleep.
My mother fervently cleans the house as if she's waging a one-woman war against dirt.