How do you spell Centripetal

Available Definitions:
1)  a. - Tending, or causing, to approach the center.
2)  a. - Expanding first at the base of the inflorescence, and proceeding in order towards the summit.
3)  a. - Having the radicle turned toward the axis of the fruit, as some embryos.
4)  a. - Progressing by changes from the exterior of a thing toward its center; as, the centripetal calcification of a bone.