Definition

1. Preposition:

   • Near or next to: Indicates proximity in space.
   • Past or through: Indicates movement past a point or through an area.
   • Not later than; at or before: Indicates a point in time as a deadline.
   • Through the agency, means, or work of: Indicates the agent performing an action or the means used.
   • According to; in conformity with: Indicates a standard, rule, or method.
   • In successive units of: Indicates measurement or quantity in units.
   • To the extent of: Indicates a degree or margin.

2. Adverb:

   • Near or at hand: In proximity.
   • Past: To and beyond a point; alongside.
   • Aside; in reserve: Away for future use.

Usage and Examples

• Preposition (Proximity):

  • She sat by the window. (She was seated next to the window.)
  • The house is by the lake. (The house is located near the lake.)

• Preposition (Means/Agent):

  • The letter was sent by post. (The means of sending the letter was the postal service.)
  • The book was written by a famous author. (The agent who performed the action of writing was the author.)

• Preposition (Time - Not later than):

  • Please submit the report by Friday. (The deadline for submission is Friday.)
  • I will be home by 6 o'clock. (I will arrive at or before 6 o'clock.)

• Preposition (According to):

  • By my watch, it's noon. (According to the time on my watch, it is noon.)
  • We must play by the rules. (We must act in conformity with the rules.)

• Adverb (Past):

  • The car drove by. (The car moved past this point.)
  • Time goes by quickly. (Time passes quickly.)

• Adverb (Aside/In reserve):

  • She has some money put by. (She has some money saved or set aside.)

Advanced Usage

• "By and by": After a short time; soon.

  • He will understand by and by. (He will understand soon.)

• "By and large": On the whole; generally.

  • By and large, the project was a success. (Generally speaking, the project was successful.)

• "By oneself": Alone; without help.

  • She built the model by herself. (She built it alone, without assistance.)

Variants and Related Words

• Bye (noun, interjection): A secondary meaning as a shortened form of "goodbye" or used in sports (e.g., a in a tournament).
  • He got a bye to the second round. (He advanced to the next round without playing.)

Synonyms

• Beside (preposition): At the side of; next to.
• Via (preposition): By way of; through.
• Per (preposition): For each; according to (used in rates).
• Before (preposition): Earlier than (in time contexts).

Related Phrases and Idioms

• By the way: Used to introduce a comment or question not directly related to the main topic.

  • By the way, did you call your mother? (Incidentally, did you call your mother?)

• By heart: From memory.

  • She learned the poem by heart. (She memorized the poem completely.)

• By chance: Accidentally; without planning.

  • We met by chance at the airport. (Our meeting was unplanned.)

• By all means: Certainly; definitely (used to give permission).

  • "May I come in?" "By all means." ("Certainly, you may.")

• By no means: Not at all; certainly not.

  • It is by no means certain. (It is definitely not certain.)

• Stand by (phrasal verb): To be ready; to wait; to support.

  • Please stand by for further instructions. (Please wait, ready for instructions.)

• Get by (phrasal verb): To manage to live or survive, often with difficulty.

  • They have just enough money to get by. (They have just enough to survive.)

Adverb

1. in reserve; not for immediate use
   • started setting aside money to buy a car
   • put something by for her old age
   • has a nest egg tucked away for a rainy day
2. so as to pass a given point
   • every hour a train goes past