cyme [ sime ] noun: a flat- or round-topped determinate inflorescence in the form of a flower cluster in which each individual flower stalk ends in a single flower and in which the first flower blooms at the top or in the center
Critical to the definition of a cyme is understanding that there are multiple flowers in the cluster, but the first one to open in the center is at the end of the main axis (usually a peduncle or inflorescence stalk), and the others that bloom after it are from lateral buds that form beneath from the axils of leaves or bracts.
The illustration to the right shows various kinds of determinate inflorescences. In each case the largest circle indicates the first terminal flower to bloom, and the subsequent ones work their way out from the center or further down the main stalk. The multiple forms show us that it can be confusing to determine what kinds of flowers are determinate, but with care and practice we can identify them.
Prior PV. 1960 “Development of the Helicoid and Scorpioid Cymes in Myosotis laxa Lehm. and Mertensia virginica L.” Proceedings of the Iowa Academy of Science, 67(1): 76-81. Available at: https://scholarworks.uni.edu/pias/vol67/iss1/11.
Weakley AS, Ludwig JC, Townsend JF. 2012. Flora of Virginia. Botanical Research Institute of Texas. pages 516, 519, 661.