Confusing, obscure or unknown Liturgical terms

I have been asked to do a series of posts on confusing Liturgical Terms. On of the first suggested for my attention was "feria". Could this have something to do with the fact that I have taken to heading my first post on ferias simply "Feria"? I don't know, but I'm more than happy to fulfill the request, so here goes.

"Feria" today,simply means "weekday", but originally it meant a day in the Roman Calendar on which slaves were not required to work and on which no court sessions were held. In the early Church it corresponded to our "Holy Day of Obligation", but has since totally lost that meaning.

In the Calendar of the Church, Sunday is "Dies Dominici", the Day of the Lord and Saturday is "Sabbato", the Sabbath. The five intervening days are "feria prima", feria secunda", etc.

In a complete reversal from the Roman usage and the early usage of the Church, the word has come to mean a day on which there is no Feast. There may be a "Commemoration" of a Saint (or Saints) who do not rank even as a Feast of the Third Class, but the Mass is of the preceding Sunday and the Divine Office is recited from the Psalter of the day, with the lessons at Mattins coming from the Proper of the Season.

More information can be found in the Catholic Encyclopædia and at Wikipedia.