The androecium is a structure that consists of stamens. Each stamen represents the male reproductive organ. Every stamen consists of a filament and an anther. When the stamens may be united into one bunch or one bundle, this condition is called monadelphous. E.g., China rose. When two bundles may be united into one bunch, this condition is called diadelphous. When more than two bundles may be united into one bunch, this condition is called polyadelphous. E.g., Citrus.
In synandrous condition, the stamens are united throughout their whole length.E.g., Benincasa
In syngenesious condition, the anthers are fused but the filaments are free.