Seax (Old English pronunciation: [ˈsæɑks]; also sax, sæx, sex, latinized sachsum) is an Old English word for "knife". In modern archaeology, the term seax is used specifically for a type of sword or dagger typical of the Germanic peoples of the Migration period and the Early Middle Ages, especially the Saxons, whose name derives from the weapon.
In heraldry, the seax is a charge consisting of a curved sword with a notched blade, appearing, for example, in the coats of arms of Essex and the former Middlesex.
Old English seax, sax and Old Frisian sax are identical with Old Saxon and Old High German saks, all from a Common Germanic *sahsą from a root *sah, *sag- "to cut" (also in , from a PIE root ). In Scandinavia, the words sax, saks or sakset all refer to scissors, which of course are used for cutting various materials. The term scramaseax or scramsax (lit. "wounding-knife") is sometimes used for disambiguation, even though it is not attested in Old English, but taken from an occurrence of scramasaxi in Gregory of Tours' History of the Franks.
The name of the roofer's tool, the zax, is a development from this word.
Amongst the shape and construction of seaxes there is a great deal of variation. The most frequent characteristics are:
In the continental Germanic area, the following types are defined for seaxes between roughly 450 and 800 AD, in chronological order: