What common email abbreviations mean
| Abbreviation | What it means | Spell it out when |
|---|---|---|
| EOD | End of day, usually the end of the workday | The time or time zone matters |
| COB | Close of business, often used as a synonym for EOD | Business hours may differ across recipients |
| EOB | End of business, another term for the end of the workday | Your group follows a different convention |
| EOM | End of message in a subject line, or end of month in finance contexts | Either meaning could fit the message |
| FYI | For your information | You need the recipient to take action |
| NRN | No reply needed | The reader may not know the abbreviation |
| TL;DR | Too long; didn't read, used to introduce a summary | The email is formal or goes to an external reader |
| ASAP | As soon as possible | Deadlines must go into the recipient's calendar |
EOD
- What it means
- End of day, usually the end of the workday
- Spell it out when
- The time or time zone matters
COB
- What it means
- Close of business, often used as a synonym for EOD
- Spell it out when
- Business hours may differ across recipients
EOB
- What it means
- End of business, another term for the end of the workday
- Spell it out when
- Your group follows a different convention
EOM
- What it means
- End of message in a subject line, or end of month in finance contexts
- Spell it out when
- Either meaning could fit the message
FYI
- What it means
- For your information
- Spell it out when
- You need the recipient to take action
NRN
- What it means
- No reply needed
- Spell it out when
- The reader may not know the abbreviation
TL;DR
- What it means
- Too long; didn't read, used to introduce a summary
- Spell it out when
- The email is formal or goes to an external reader
ASAP
- What it means
- As soon as possible
- Spell it out when
- Deadlines must go into the recipient's calendar
When to spell out an email abbreviation
Spell out an email abbreviation when you're writing to a client, a new colleague, or anyone who might not share your team's shorthand. You can use familiar abbreviations without explanation inside a team that already uses them consistently, but don't make an outside reader guess. A useful default is to explain specialist terms and shorthand on first use, then put the abbreviation in parentheses if you'll use it again. Write “by the end of the day (EOD) on Tuesday, Toronto time” or “for your information (FYI)” the first time it appears.
EOD, COB, and EOB often mean the same thing
COB and EOB are synonyms for business EOD, according to the Cambridge Dictionary. Your workplace may define them differently, but there is no universal rule that COB is earlier or firmer than EOD.
Inside a group with shared hours, “I'll send the revised file by EOD Thursday” may be clear enough. When the exact time matters, write “I'll send the revised file by Thursday, August 27, at 4:00 p.m. Eastern Time.”
Write deadlines across time zones
Greater time-zone separation was associated with more work communication outside regular hours among 12,038 employees at one multinational firm in a 2024 study. When you write EOD without a zone, the reader has to guess whose clock you mean.
A manager in New York writes “Send the final file by EOD Friday” to a contractor in Los Angeles.
One Friday afternoon on a single timeline. “EOD Friday” marks two moments three hours apart, 5:00 p.m. in New York and 5:00 p.m. in Los Angeles. A deadline written with the date, time, and zone marks one moment.
Friday, August 28 · 5:00 p.m. in New York · 2:00 p.m. in Los Angeles
FYI, NRN, TL;DR, EOM, and ASAP
- FYI: When assigning work, don't introduce the request with FYI. Change “FYI, revised numbers attached. Can you recalculate sections 4–7 today?” to “Please recalculate sections 4–7 by Tuesday, August 25, at 2:00 p.m. Eastern Time. I need the totals for the 3:00 p.m. review.”
- NRN: With an unfamiliar reader, write “No reply is needed.”
- TL;DR: Use “Summary” in a formal email or with a reader who may not know the label.
- EOM: For a finance deadline, change “Reconciliation due EOM” to “Please finish the reconciliation by Monday, August 31, at 5:00 p.m. Eastern Time.” In a subject line, use EOM only with people who know it. Otherwise, put the update in the message body.
- ASAP: Write “Could you send this ASAP?” as “Could you send this by Tuesday, August 25, at 11:00 a.m. Eastern Time? I need to include it in the noon client review.”
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Questions, answered.
In business use, EOD usually means the end of the workday. The exact cutoff depends on the workplace and time zone, so give a clock time when the hour matters.