“Most flowers are based on a particular numerical plan — that is, on patterns of three, four, five, or various multiples of those numbers. The ending -merous, along with a numerical prefix, is used to indicate a flower’s numerical plan.

“For example, a flower might have four sepals, four petals, eight stamens, and four carpels; such a flower would be described as 4-merous.” — Judd et al., Plant Systematics, a Phylogenetic Approach

“Merosity refers to the number of parts per whorl or cycle.” — Simpson, Plant Systematics