Octave in liturgical usage has two senses. In the first sense, it is the eighth day following a major feast, particularly in the Catholic, Eastern Orthodox and Anglican liturgal calendars. In the late Middle Ages the second sense of octave developed as an eight-day festival with a specific liturgy).

The term is used in both senses today. In the former sense the Octave of Christmas among the Western churches always falls on January 1st and in the Catholic Church is the Solemnity of Mary, a holy day of obligation in the United States. Likewise, the Octave of Pentecost (Sunday) is Trinity Sunday.

In the second sense, that is an eight-celebration, the term is most commonly used today to refer to the Octave of Easter, the week (and particularly the Sunday) following Easter Sunday, which is the most vividly celebrated octave in the Catholic liturgical year. Each of the days in the Octave of Easter is celebrated with the rites of Easter Sunday, a period sometimes referred to as Easter Week, or the Week of Sundays. The Sunday following Easter Sunday is also called the Octave of Easter, meaning "the eighth day."

Oktáv | Oktav (Liturgie)