A homily (from Greek ὁμιλία, homilía) is a commentary that follows a reading of scripture, giving the "public explanation of a sacred doctrine" or text. The works of Origen and John Chrysostom (known as Paschal Homily) are considered exemplary forms of Christian homily.
In Catholic, Anglican, Lutheran, and Eastern Orthodox churches, a homily is usually given during Mass (Divine Liturgy or Holy Qurbana for Orthodox and Eastern Catholic Churches, and Divine Service for the Lutheran Church) at the end of the Liturgy of the Word. Many people consider it synonymous with a sermon.
The English word homily is derived from the Ancient Greek word ὁμιλία homilia, which means intercourse or interaction with other people (derived from the word homilos, meaning "a gathering"). The word is used in 1 Corinthians 15:33 ("wicked homiliai corrupt good morals"). The related verb is used in Luke 24:14 (as homiloun), and in Acts 24:26 (as homilei), both used in the sense of "speaking with". The word later came to have a more technical sense. According to The Catholic Encyclopedia, Origen was the first to distinguish between logos (sermo) and homilia (tractatus).
The General Instruction of the Roman Missal (GIRM), the official document governing the celebration of Mass, states that:
65. The Homily is part of the Liturgy and is strongly recommended, for it is necessary for the nurturing of the Christian life. It should be an exposition of some aspect of the readings from Sacred Scripture or of another text from the Ordinary or from the Proper of the Mass of the day and should take into account both the mystery being celebrated and the particular needs of the listeners.
Contemporary Protestant clergy often use the term 'homily' to describe a short sermon, such as one created for a wedding or funeral.
In colloquial, non-religious, usage, homily often means a sermon concerning a practical matter, a moralizing lecture or admonition, or an inspirational saying or platitude, but sermon is the more appropriate word in these cases.