The cover of a tulip flower bud parts as the flower opens, but the parts don't just peel back like other bud covers or "sepals." They continue to grow and color, ending up nearly indistinguishable from the petals. Could you tell that the pretty pink segment at far left and right, below, was just a bud cover? Such a tealented sepal earns the name "tepal."
Other plants, such as lilies, iris and daylily (below) have tepals. A daylily has three petals (foreground) and three tepals (behind).