A day on which the people, especially the slaves, were not obliged to work, and on which there were no court sessions
Feria (Lat. for "free day"), a day on which the people, especially the slaves, were not obliged to work, and on which there were no court sessions. In ancient Roman times the feria: publicce, legal holidays, were either stativce, recurring regularly (e.g. the Saturnalia), conceptivw, i. e. movable, or imperativce, i.e. appointed for special occasions. When Christianity spread, the feriae were ordered for religious rest, to celebrate the feasts instituted for worship by the Church. The faithful were obliged on those days to attend Mass in their parish church; such assemblies gradually led to mercantile enterprise, partly from necessity and partly for the sake of convenience. This custom in time introduced those market gatherings which the Germans call Messen, and the English call fairs. They were fixed on saints' days (e.g. St. Barr's fair, St. Germanus's fair, St. Wenn's fair, etc.).
Today the term feria is used to denote the days of the week with the exception of Sunday and Saturday. Various reasons are given for this terminology. The Roman Breviary, in the sixth lesson for December 31, says that Pope St. Silvester ordered the continuance of the already existing custom, "that the clergy, daily abstaining from earthly cares, would be free to serve God alone". Others believe that the Church simply Christianized a Jewish practice. The Jews frequently counted the days from their Sabbath, and so we find in the Gospels such expressions as una Sabbati and prima Sabbati, the first from the Sabbath. The early Christians reckoned the days after Easter in this fashion, but, since all the days of Easter week were holy days, they called Easter Monday, not the first day after Easter, but the second feria or feast day; and since every Sunday is the dies Dominica, a lesser Easter day, the custom prevailed to call each Monday a feria secunda, and so on for the rest of the week.
The ecclesiastical style of naming the week days was adopted by no nation except the Portuguese, who alone use the terms Segunda Feira etc. The old use of the word feria, for feast day, is lost, except in the derivative feriatio, which is equivalent to our of obligation. Today those days are called ferial upon which no feast is celebrated. Feriae are either major or minor. The major, which must have at least a commemoration, even on the highest feasts, are the feriae of Advent and Lent, the Ember days, and the Monday of Rogation week; the others are called minor. Of the major feriae Ash Wednesday and the days of Holy Week are privileged, so that their office must be taken, no matter what feast may occur.