Inflorescence and Umbel

Inflorescence noun - The flowering part of a plant or arrangement of flowers on a stalk.

Umbel and inflorescence are semantically related. In some cases you can replace term "Umbel" with "Inflorescence", this nouns are similar.

Umbel noun - Flat-topped or rounded inflorescence characteristic of the family Umbelliferae in which the individual flower stalks arise from about the same point; youngest flowers are at the center.

Inflorescence and umbel are semantically related. You can use "Inflorescence" instead a noun "Umbel".