n.
1.the earliest eon in the history of the Earth from the first accretion of planetary material (around 4,600 million years ago) until the date of the oldest known rocks (about 3,800 million years ago)
Idiom of the Day
end up (doing something)
to do something that one had not planned to do, to finally be or do something
I ended up studying rather than going to a movie last night. The man ended up getting married to his neighbor.