What is the meaning of the word "day"?

Definitions:

a period of opportunity noun
- Every person deserves their day in court.
an era of existence or influence noun
- in the day of the dinosaurs
some point or period in time noun
- it should arrive any day now
the period of time taken by a particular planet (e.g. Mars) to make a complete rotation on its axis noun
- how long is a day on Jupiter?
the recurring hours when you are not sleeping, especially those when you are working noun
- My day began early this morning.
the time after sunrise and before sunset while it is light outside noun
- the dawn turned night into day
time for Earth to make a complete rotation on its axis noun
- two days later they left