Wednesday is the day of the week between Tuesday and Thursday. According to international standard ISO 8601, it is the third day of the week. In countries which have Friday as their holiday, Wednesday is the fifth day of the week. In countries which use the Sunday-first convention, and in both the Islamic and Jewish calendars, Wednesday is the fourth day of the week.
In English, the name is derived from Old English Wōdnesdæg and Middle English Wednesdei, 'day of Woden', reflecting the religion practiced by the Anglo-Saxons, the English equivalent to the Norse god Odin. In many Romance languages, such as the French mercredi, Spanish miércoles or Italian mercoledì, the day's name is a calque of Latin dies Mercurii 'day of Mercury'.
Wednesday is in the middle of the common Western five-day workweek that starts on Monday and finishes on Friday.
See Names of the days of the week for more on naming conventions.
The name Wednesday continues Middle English Wednesdei. Old English still had wōdnesdæg, which would be continued as *Wodnesday (but Old Frisian has an attested wednesdei). By the early 13th century, the i-mutated form was introduced unetymologically.
The name is a calque of the Latin dies Mercurii 'day of Mercury', reflecting the fact that the Germanic god Woden (Wodanaz or Odin) during the Roman era was interpreted as "Germanic Mercury".
The Latin name dates to the late 2nd or early 3rd century. It is a calque of Greek ἡμέρα Ἕρμου (heméra Hérmou), a term first attested, together with the system of naming the seven weekdays after the seven classical planets, in the Anthologiarum by Vettius Valens (c. AD 170).
The Latin name is reflected directly in the weekday name in most modern Romance languages: mércuris (Sardinian), mercredi (French), mercoledì (Italian), miércoles (Spanish), miercuri (Romanian), dimecres (Catalan), marcuri or mercuri (Corsican), mèrcore (Venetian). In Welsh it is Dydd Mercher, meaning 'Mercury's Day'.
The Dutch name for the day, woensdag, has the same etymology as English Wednesday; it comes from Middle Dutch wodenesdag, woedensdag ('Wodan's day').