The ancient terms for galleys was based on the numbers of rows or rowers plying the oars, not the number of rows of oars.

The basic design of two or three rows of oars remained the same, but more rowers were added to each oar.

Not only the triangular, but also the quadrilateral version were known, used for centuries (mostly on smaller craft) in parallel with square sails.

The trireme was an advanced ship that was expensive to build and to maintain due its large crew.

The last known reference to triremes in battle is dated to 324 at the battle of the Hellespont.

To counter the threat, local rulers began to build large oared vessels, some with up to 30 pairs of oars, that were larger, faster and with higher sides than Viking ships.