Umbel:  An inflorescence (often flat-topped) with the flower stalks arising from a single point on the peduncle (inflorescence stalk) and resembling the spokes of an umbrella.  Example: dill, Queen Anne’s lace.

Valvate: for buds, the scales meeting by the edges without overlapping

Whorl: Arrangement of three or more leaves at a node.  Also a ring of floral structures.