Advent vs Second Advent

Advent and Second Advent both are nouns.

Word	Noun	Adjective	Verb	Adverb
Advent	Yes	No	No	No
Second Advent	Yes	No	No	No

As nouns, Advent and Second Advent are synonyms defined as:

Advent and Second Advent: (Christian theology) the reappearance of Jesus as judge for the Last Judgment

Other synonyms of Advent include Parousia, Second Coming, Second Coming of Christ.

Advent (noun)	Second Advent (noun)
(Christian theology) the reappearance of Jesus as judge for the Last Judgment	(Christian theology) the reappearance of Jesus as judge for the Last Judgment
the season including the four Sundays preceding Christmas