Kopis

The kopis had a single-edged blade that pitched forward towards the point, the edge being concave on the part of the sword nearest the hilt, but swelling to convexity towards the tip.

This shape, often termed "recurved", distributes the weight in such a way that the kopis was capable of delivering a blow with the momentum of an axe, whilst maintaining the long cutting edge of a sword and some facility to execute a thrust.

[6] The Ancient Greeks often used single-edged blades in warfare, as attested to by art and literature; however, the double-edged, straight, and more martially versatile xiphos is more widely represented.

Greek heavy infantry hoplites favored straight swords, but the downward curve of the kopis made it especially suited to mounted warfare.

[7] The precise wording of Xenophon's description suggests the possibility that the kopis was regarded as a specific variant within a more general class, with the term makhaira denoting any single-edged cutting sword.

Greek hoplite (standing) fighting against a Persian archer. Both are using a kopis. Depiction in ancient kylix , 5th century BC, National Archaeological Museum of Athens.
Greek kopis, 5th–4th centuries BC, iron, Metropolitan Museum of Art.
Modern reproduction of a kopis