(from δια, twice, and ἀνήρ, a man), the name of the second class in Linnaeus's sexual system, consisting of hermaphrodite plants; which, as the name imports, have flowers with two stamens or male organs.

The orders in this class are three, derived from the number of styles or female parts. Most plants with two stamens have one style; as jessamine, lilac, privet, veronica, and balsam alaternus; vernal grass has two styles; pepper, three.