The labellum can be variously segmented into lobes resulting from indentation of the margin.
Unlobed: the labellum margins are smooth (entire).
Two-lobed: the labellum apex is deeply divided into two lobes which can remain close together or spread widely apart.
Three-lobed: the labellum is divided into three lobes, the basal two lobes are known as the lateral lobes and the upper lobe is called the midlobe.
Four-lobed: in a few orchids that have well developed lateral lobes the midlobe is deeply divided, the whole structure appearing as if four lobed.