by

1. Close to; next to: the window by the door.
2. With the use or help of; through: We came by the back road.
3. Up to and beyond; past: We drove by the house.
4. At or to: stopped by the bakery; came by the house.
5. In the period of; during: sleeping by day.
6. Not later than: by 5:30 P.M.
7. 1. In the amount of: letters by the thousands.
   2. To the extent of: shorter by two inches.
8. 1. According to: played by the rules.
   2. With respect to: siblings by blood.
9. In the name of: swore by the Bible to tell the truth.
10. Through the agency or action of: was killed by a bullet.
11. Used to indicate a succession of specified individuals, groups, or quantities: One by one they left. They were persuaded little by little.
12. 1. Used in multiplication and division: Multiply 4 by 6 to get 24.
    2. Used with measurements: a room 12 by 18 feet.
    3. Toward. Used to express direction with points of the compass: south by east.

1. On hand; nearby: Stand by.
2. Aside; away: We put it by for later.
3. Up to, alongside, and past: The car raced by.
4. At or to one's home or current location: Stop by later today.
5. Into the past: as years go by.

by oneself

1. Without company; alone: went by herself.
2. Without help: wrote the book by myself.

[Middle English, from Old English bī, be.]