AT vs BY in English: when to use?
AT vs BY Prepositions in English: Complete Grammar Guide with Examples, Practice Exercises and Memory Tricks
Master the difference between AT and BY prepositions in English with clear examples, practice exercises, and expert tips. Perfect for English learners at all levels.
Quick Answer: AT vs BY in 30 Seconds ⚡
AT = Specific point in time
- “The meeting starts at 9 AM”
- “I’ll call you at lunch”
BY = Deadline (no later than)
- “Finish your homework by Friday”
- “Be home by midnight”
Ultimate Test: 15 Questions on AT vs BY 📝
Instructions: Choose the correct preposition (AT or BY) for each sentence. Check your answers at the end!
Understanding AT: The Precise Time Preposition
When to Use AT
AT is your go-to preposition for exact times and specific moments. Think of it as a spotlight pointing to one precise moment on the timeline.
1. Clock Times (Hours and Minutes)
- At 7 a.m. ✅
- At sunrise ✅
- At noon ✅
- At sunset ✅
- At midnight ✅
- At 5 o’clock ✅
- At 14:09 ✅
2. Specific Times of Day
- At night ✅ (Note: We say “at night” but “in the morning/afternoon/evening”)
- At breakfast ✅
- At lunchtime ✅
- At dinnertime ✅
- At bedtime ✅
3. Special Moments and Occasions
- At Christmas ✅ (referring to the holiday period)
- At New Year ✅
- At the moment ✅
- At present ✅
- At the same time ✅
- At the weekend ✅ (British English)
- At a young age ✅
4. Beginning and End Points
- At first ✅
- At that time ✅
- At every hour ✅
Common AT Mistakes to Avoid ❌
In the moment→ At the moment ✅On Christmas→ At Christmas ✅ (for the holiday period)At morning→ In the morning ✅At Monday→ On Monday ✅
Understanding BY: The Deadline Preposition
When to Use BY
BY means “no later than” or “before or at that time”. It sets a clear deadline or time limit.
1. Deadlines with Times
- By 5 p.m. ✅
- By 7 o’clock ✅
- By noon ✅
- By midnight ✅
- By evening ✅
- By lunchtime ✅
2. Deadlines with Days
- By Monday ✅
- By tomorrow ✅
- By next week ✅
- By Sunday night ✅
- By Friday morning ✅
- By the weekend ✅
3. Deadlines with Dates and Months
- By 2025 ✅
- By the end of the month ✅
- By the first of January ✅
- By the end of the day ✅
4. Process Completion
- By the time you wake up ✅
- By the time he arrives ✅
- By the deadline ✅
- By now ✅
Key Point About BY 🎯
BY always implies that something can happen earlier than the stated time. If you say “Submit your report by Friday,” it means Friday is the LATEST acceptable time, but Tuesday or Wednesday would be even better!
AT vs BY: Side-by-Side Comparison
| AT (Specific Time) | BY (Deadline) |
|---|---|
| The store opens at 9 AM | Please arrive by 9 AM |
| Call me at lunch | Finish eating by lunch |
| We met at Christmas | Send gifts by Christmas |
| I woke up at 6:30 | Wake up by 6:30 |
| The meeting starts at 2 PM | Join the meeting by 2 PM |
Memory Tricks to Never Forget! 🧠
For AT:
“AT = Accurate Time”
- Think of AT as an arrow pointing to an exact spot on a clock
For BY:
“BY = Before Yikes!”
- Think of BY as a warning: “Do it before it’s too late!”
Visual Memory Aid:
- AT = 📍 (exact pinpoint location in time)
- BY = ⏰ (alarm clock warning of deadline)
Common Real-Life Situations
Work and Business
- “The conference call starts at 10 AM sharp”
- “Please submit your timesheet by Friday”
- “I’ll be in the office at 8:30″
- “All reports must be ready by the end of the month”
School and Education
- “Class begins at 9:15″
- “Homework is due by Tuesday”
- “The exam starts at noon”
- “Registration closes by September 1st”
Daily Life
- “Dinner is at 6 PM”
- “Be home by midnight”
- “The movie starts at 7:30″
- “Return the car by Monday morning”
Advanced Usage: Tricky Situations
Christmas Example
- “At Christmas, we visit family” (during the holiday period)
- “On Christmas Day, we exchange gifts” (specific day)
- “By Christmas, all shopping should be done” (deadline)
Weekend Variations
- British English: “At the weekend” (during the weekend)
- American English: “On the weekend” (during the weekend)
- Both varieties: “By the weekend” (deadline)
Night vs Evening
- “At night” ✅ (correct)
- “In the evening” ✅ (correct)
“In the night”(incorrect for general time)
Practice Exercises
Exercise 1: Fill in the Blanks
Choose AT or BY:
- The train arrives _____ 3:30 PM.
- Please finish your work _____ Friday.
- I always feel tired _____ night.
- Submit your application _____ the deadline.
- The meeting starts _____ noon.
- Be ready _____ 8 AM tomorrow.
- We celebrate _____ New Year.
- Send the email _____ end of day.
Exercise 2: Error Correction
Fix these common mistakes:
- I’ll call you in the moment. → _____
- Finish this on Friday. (meaning: no later than) → _____
- The party starts by 8 PM. (meaning: exactly) → _____
- We always travel in Christmas. → _____
Exercise 3: Real-Life Scenarios
Complete with AT or BY:
- “Doctor’s appointment is _____ 2:15 PM”
- “Please arrive _____ 15 minutes before your appointment”
- “Pharmacy closes _____ 6 PM” (deadline for getting medicine)
- “Take your medication _____ bedtime”
Answer Key
Exercise 1:
- at (specific time)
- by (deadline)
- at (specific time period)
- by (deadline)
- at (specific time)
- by (deadline)
- at (holiday period)
- by (deadline)
Exercise 2:
- I’ll call you at the moment.
- Finish this by Friday.
- The party starts at 8 PM.
- We always travel at Christmas.
Exercise 3:
- at (specific appointment time)
- by (deadline for arrival)
- by (deadline)
- at (specific time)
Pro Tips for Mastery 🌟
- Listen for context: If someone sounds urgent or mentions consequences, they probably mean BY (deadline)
- Clock test: If you can point to an exact time on a clock face, use AT
- Flexibility test: If there’s flexibility in timing (earlier is better), use BY
- Learn phrases as chunks: Memorize “at the moment,” “by the end,” “at Christmas” as complete units
- Practice daily: Use both prepositions in your daily English conversations
Regional Differences: British vs American English
| Situation | British English | American English |
|---|---|---|
| Weekend | at the weekend | on the weekend |
| Hospital | at hospital | in the hospital |
| University | at university | in college |
Note: Both AT and BY usage for deadlines and specific times remains the same across all English varieties.
Quick Reference Card 📋
Use AT for:
- Clock times (at 3 PM)
- Mealtimes (at lunch)
- Specific moments (at sunrise)
- Holiday periods (at Christmas)
Use BY for:
- Deadlines (by Friday)
- “No later than” situations (by 5 PM)
- Time limits (by the end of the month)
- Completion points (by now)
Red Flags:
- Never say “at Monday” → use “on Monday”
- Never say “by 3 PM” when you mean exactly 3 PM → use “at 3 PM”
- Remember: “at night” but “in the morning”
Final Test: Are You Ready? 🎯
Can you explain the difference between these sentences?
- “Meet me at 6 PM” vs “Meet me by 6 PM”
- “Call at lunch” vs “Call by lunch”
- “At Christmas” vs “By Christmas”
If you understand that the first option in each pair means an exact time and the second means a deadline, congratulations! You’ve mastered AT vs BY! 🎉
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