inflorescence vs umbel

inflorescence and umbel both are nouns.

Word	Noun	Adjective	Verb	Adverb
inflorescence	Yes	No	No	No
umbel	Yes	No	No	No

As nouns, umbel is a hyponym of inflorescence; that is, umbel is a word with a more specific, narrower meaning than inflorescence:

inflorescence: the flowering part of a plant or arrangement of flowers on a stalk
umbel: 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

Other hyponyms of inflorescence include flower head, ament, catkin, corymb, flower cluster, cyme, spike.

inflorescence (noun)	umbel (noun)
the flowering part of a plant or arrangement of flowers on a stalk	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
the time and process of budding and unfolding of blossoms