A coming or arrival; a coming into use.
Example:
The advent of spring was always marked by the blue crocuses pushing up through the snow.
Advent includes the prefix ad-, "to or toward," and thus means basically a "coming toward." The Advent season in the Christian religion consists of the weeks leading up to Christmas, when the coming of Christ is anticipated. The advent of mass printing with Gutenberg's printing press in the mid-15th century had an enormous effect on European society and politics; the advent of the computer in the mid-20th century has promised to change ours even more profoundly.