The word inflorescence is a noun. It is a flower cluster.
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cymose inflorescence (cyme; definite inflorescence) A type of flowering shoot (see inflorescence) in which the first-formed flower develops from the growing region at the top of the flower stalk
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The type of infloresence a lilac has is called a panicle. This
means that lilacs have many flowers on a spike clustered
together.