How to Spell Per Diem | Hyphen Rules And Copy Fixes

You’ve seen it in travel emails, job offers, and expense reports. Then you pause: is it “per-diem,” “perdiem,” or something else? The good news is that the core spelling stays steady. Once you know the handful of edge cases, you can write it cleanly every time.

This page gives you the spelling, the hyphen rule, and quick edits that work in real writing. You’ll also get ready-to-copy samples for policies and messages, plus a short checklist you can run before you hit send.

If you landed here because you searched “how to spell per diem,” you’re in the right spot. You’ll leave with a spelling rule you can apply without second-guessing.

Per Diem Spelling At A Glance

Use Case	Correct Form	Notes
Noun for daily allowance	per diem	Two words, lowercase in sentences
Adjective before a noun	per-diem rate	Hyphen joins the phrase when it modifies a noun
Plural allowances	per diems	Add s; no apostrophe
Start of a sentence	Per diem	Cap only because it starts the sentence
Headings and titles	Per Diem	Match your title case style, still two words
Legal or policy wording	per diem	Keep consistent within the document
Common wrong forms	perdiem / per-diem	One word is wrong; hyphen as a noun is a style choice, not the default
Latin italics question	per diem	Often roman type; italics depend on house style

What “Per Diem” Means In Plain English

Per diem is a Latin phrase that means “per day.” In modern writing it usually points to a daily allowance or a daily rate. Think meals while traveling, lodging caps, or a set amount paid for each day on a trip.

Because it shows up in money and policy contexts, small spelling slips can look sloppy. A reader may wonder if you copied the term from somewhere else or if your policy text was stitched together. Clean spelling makes the document feel consistent and easier to trust.

How to Spell Per Diem In Everyday Writing

Write it as two separate words: per diem. In normal sentences it stays lowercase. That’s the spelling you’ll see in dictionaries and in most workplace writing.

Example: “We reimburse meals using a per diem for each travel day.”

If you’re building a template, lock the spelling in one place and reuse it. Copy-paste beats retyping, since retyping is where “perdiem” sneaks in.

Capitalization Rules That Stay Simple

In the middle of a sentence, keep it lowercase: per diem. Capitalize it only when standard grammar forces a capital, like the start of a sentence. In headings, use the same title style you use for other words, but keep it two words.

• Sentence middle: “The per diem pays for meals.”
• Sentence start: “Per diem rates change by city.”
• Heading: “Per Diem Rates By Day”

Italics And Quotation Marks

Many Latin phrases have become everyday English, so writers often leave them in regular type. Some house styles still italicize Latin on first use, then switch to regular type after the reader has seen it once.

If you write for a team, follow the team’s style sheet. If you don’t have one, pick a single approach and stick with it across the page. Mixing italics and plain text in the same doc looks like two editors fought over it.

When To Use A Hyphen With Per Diem

The hyphen shows up when the phrase acts as one modifier right before a noun. That pattern is common in English: a two-word phrase becomes one “unit” when it describes the next word.

Use the hyphen in cases like these:

• per-diem rate
• per-diem allowance
• per-diem reimbursement

Skip the hyphen when the phrase stands on its own as a noun:

• “The per diem is $60.”
• “Submit receipts that exceed the per diem.”

Style guides don’t all treat hyphenation the same way, so you may see “per diem rate” without a hyphen. If your workplace has a standard, match it. If not, the hyphen version reads cleanly because it signals that “per” and “diem” belong together as a modifier.

Per Diem As A Noun Vs. An Adjective

Here’s a quick test. If you can swap in “daily” without changing the sentence shape, you’re often using an adjective form. That’s the spot where the hyphen is most useful.

Compare:

• Noun: “Your per diem starts on Monday.”
• Adjective: “Your per-diem rate starts on Monday.”

Plural, Possessive, And Other Tricky Forms

The plural is straightforward: per diems. Add an s to the end of the phrase. Avoid “per diem’s,” since that apostrophe signals possession, not plural.

Possessive forms are rare, but they can appear in tight policy writing. If you need possession, put the apostrophe after the s: “per diems’ limits.” In most cases you can rewrite to dodge the possessive and keep the sentence smoother: “limits for per diems.”

Per Diem As A Compound In Job Posts

Job listings sometimes treat it like a fixed label: “Per Diem Nurse” or “Per Diem Shift.” That’s a title-style choice, not a spelling change. In body text you can still write “per diem shifts” or “a per diem role,” depending on your tone and the doc type.

Spelling Per Diem In Class Notes And Academic Papers

In school writing, the safest move is consistency. Pick one presentation and stick to it through the whole draft: either plain text per diem or italics on first use, then plain text after. Your instructor may have a style preference, so check the rubric or the department handout if you have one.

When you define the term, write the meaning in plain words right after it. That keeps the reader from hunting for a definition. Example: “The company paid a per diem, a set amount per day, to pay for meals and incidental costs.”

If you cite a source that capitalizes it in a title, keep the capitalization inside the title only. In your own sentences, return to lowercase per diem.

Where You’ll See “Per Diem” In Official Writing

Public agencies and travel programs use the term often, since it ties to reimbursement caps. If you handle U.S. government travel, the GSA per diem rates pages show consistent spelling and let you copy the term with confidence.

Dictionaries are also a clean reference point when a teammate argues about the hyphen or the plural. The Merriam-Webster entry for per diem is a quick check for spelling and basic usage.

Common Mistakes And Fast Fixes

Most errors fall into a few buckets. If you know the buckets, you can spot the issue in a blink.

One-Word “Perdiem”

This one often comes from note-taking or from older internal docs that were typed in a hurry. Fix it by splitting the word into two. In Word or Google Docs, a find-and-replace pass can clean an entire policy in seconds.

Hyphen Used As The Noun Form

Writers sometimes drop “per-diem” into a sentence as the noun, then keep doing it to stay consistent. That choice won’t confuse most readers, but it’s less common in modern plain writing. If you want a safe default, keep the noun as “per diem” and save the hyphen for the modifier form.

Random Capitals Inside A Sentence

“Per Diem” in mid-sentence can make it look like a product name. If you’re not naming a role or a program, keep it lowercase. A fast trick: scan your doc for “Per Diem” and check whether it sits in a heading or in a proper name. If not, change it.

Plural With An Apostrophe

“Per diem’s” reads like “the per diem’s amount,” which is possession. If you mean more than one allowance, use “per diems.” If you’re unsure, read the sentence out loud. If you hear “many,” skip the apostrophe.

Using Per Diem In Email, Policy, And Resume Copy

This is where spelling details pay off, since these docs get shared and reused. Use the samples below as a starting point, then adjust the numbers and rules to match your job or school context.

Email Line For A Trip

“Your per diem is $60 per travel day. Lodging is billed separately.”

Policy Line For Reimbursement

“Meals are paid with a per diem. Receipts are required only for expenses above the per diem.”

Resume Or Profile Line

“Managed travel bookings and per diem tracking for a 12-person field team.”

If you use a hyphen in your resume, use it only when the phrase modifies a noun: “per-diem tracking,” “per-diem reimbursements.” Then keep the rest of the doc aligned to that choice.

If you’re teaching, grading, or writing an assignment, the question “how to spell per diem” comes up a lot in travel and accounting topics.

Proofreading Steps That Catch Per Diem Errors

Spell-check tools are decent, but they miss style choices. A short manual pass catches the stuff that software lets slide.

Run A Targeted Search

Search for these strings: “perdiem,” “Per Diem” (in body text), and “per-diem” (used as a noun). Each hit gives you a spot to decide what you meant, then make it consistent.

Check The Word Right After It

If the next word is a noun like “rate,” “allowance,” or “reimbursement,” the hyphen form often reads best: per-diem rate. If there’s no noun right after it, stick with per diem.

Add It To Your Dictionary If Needed

Some spell-checkers flag Latin terms or split the phrase in odd ways. Add “per diem” to your custom dictionary. Then your editor stops nagging you while you work through the rest of the document.

Per Diem Editing Checklist

Check	What To Do	Mini Sample
Two-word spelling	Replace one-word “perdiem” with two words	per diem
Lowercase in sentences	Use caps only at sentence start or in titles	the per diem
Hyphen as modifier	Hyphenate when it sits right before a noun	per-diem rate
No hyphen as noun	Drop the hyphen when the phrase stands alone	the per diem
Plural without apostrophe	Add s to the end of the phrase	per diems
Consistency across the doc	Pick one hyphen rule and apply it everywhere	rate vs allowance
Template safety	Store a correct line and paste it each time	copy from policy

A quick trick: type per diem once, copy it, then paste it where you need it. Your fingers stay honest, and typos disappear on repeat.

Quick Reference You Can Paste Into Your Notes

Write per diem as two words. Keep it lowercase in sentences. Use per-diem when it modifies a noun right after it. Plural is per diems.

If you’re updating a shared policy, run a search, fix every variant, then save the clean version as the new template. That way the spelling stays steady across emails, PDFs, and forms.