Advent is a season of the liturgical year observed in many Christian churches as a time of expectant waiting and preparation for both the celebration of the Nativity of Jesus at Christmas and the return of Jesus at the Second Coming.
The word season in this two-word phrase typically covers the whole gamut of holidays packed into the last month and a half of the year, from Thanksgiving to Christmas, Hanukkah to Kwanzaa, and of course the new year too. The greetings, on the other hand, are friendly regards or wishes.
