Preposition: "By"
'By' का प्रयोग

Agent, Method, Time, and Place.

Concept: "By" is a versatile preposition. It can show who did an action (Agent), how it was done (Method), a deadline (Time), or nearness (Place).
(By का प्रयोग कर्ता, साधन, समय सीमा, या निकटता बताने के लिए होता है।)

1. The Agent (Passive Voice - के द्वारा)

Used to show who performed the action in Passive Voice.

English Sentence	Hindi Meaning
The letter was written by Ram.	पत्र राम के द्वारा लिखा गया था।
The snake was killed by him.	साँप उसके द्वारा मारा गया।
I was taught by a great teacher.	मुझे एक महान शिक्षक ने (के द्वारा) पढ़ाया।

2. Method / Transport (से / के माध्यम से)

Used to show how something happens or how we travel. (No 'a/the' is used here).

English Sentence	Hindi Meaning
I go to school by bus.	मैं बस से स्कूल जाता हूँ।
He sent the money by check.	उसने चेक से पैसे भेजे।
She pays by credit card.	वह क्रेडिट कार्ड से भुगतान करती है।

3. Time Limit / Deadline (तक)

Used to mean "not later than" a specific time.

English Sentence	Hindi Meaning
Submit the work by 5 PM.	काम 5 बजे तक जमा करें।
I will be back by Monday.	मैं सोमवार तक वापस आ जाऊँगा।

4. Place (Near / Beside - पास / बगल में)

Used to show something is very close to something else.

He sat by me. (वह मेरे पास/बगल में बैठा।)
There is a tree by the river. (नदी के किनारे एक पेड़ है।)

Difference: By vs With