Mondays or Monday’s: Which Is Correct?

Mondays (no apostrophe) is the plural — more than one Monday: “I work Mondays.” Monday’s (with apostrophe) is either the possessive — ” Monday’s schedule” (the schedule of Monday) — or a contraction of Monday is / Monday has: “Monday’s going to be busy.” The apostrophe never makes a plural, so “open Monday’s” on a shop sign is the classic greengrocer’s apostrophe: widespread, but nonstandard in edited writing.

Mondays: The Plural

When you mean “more than one Monday,” the spelling is Mondays — just add s, no apostrophe. Collins’s entry for Monday gives the word forms as “plural Mondays,” and the pattern is the same for every day of the week: Tuesdays, Wednesdays, Fridays.

The plural shows up in two main constructions. The habitual: “I work Mondays” (every Monday, as a rule), “the shop opens late on Mondays.” And the counted: “we’ve had three rainy Mondays in a row,” “two of the last four Mondays were holidays.” In both, no apostrophe — an apostrophe never forms a plural in standard English.

Capitalization is non-negotiable: days of the week are proper nouns, so it’s always Mondays, never “mondays.” (The one systematic exception is some technical or styled contexts, but in normal writing, capitalize.)

Monday’s: Possessive or Contraction

Monday’s with the apostrophe does two legitimate jobs — and neither of them is the plural.

Job 1: singular possessive. The schedule, weather, or mood belonging to (one) Monday: “Monday’s forecast looks grim,” “we’ll follow Monday’s agenda,” “that was Monday’s big story.” The apostrophe-s marks possession, exactly as in “the dog’s dinner.”

Job 2: contraction. Monday’s = Monday is or Monday has: “Monday’s going to be hectic” (Monday is), “Monday’s been a long day” (Monday has). This is conversational — fine in dialogue, emails, and informal writing; recast it in formal prose (“Monday is going to be hectic”).

And the form people forget: the plural possessive. The early starts belonging to many Mondays are “those Mondays’ early starts” — plural Mondays first, then the apostrophe after the s. It’s rare in practice (you’d usually rephrase: “the early starts every Monday bring”), but it’s the correct form when you need it.

Form	Job	Example
Mondays	Plural	“I dread Mondays.”
Monday’s	Singular possessive	“Monday’s meeting ran long.”
Monday’s	Contraction	“Monday’s a fresh start.” (= Monday is)
Mondays’	Plural possessive	“Those Mondays’ deadlines piled up.”

The Greengrocer’s Apostrophe: An Honest Caveat

“Open Monday’s,” “closed Sunday’s,” “fresh bagel’s” — the stray apostrophe in plurals is so common on shop signs and market stalls that it has a name: the greengrocer’s apostrophe. Here’s the honest position: in edited, standard English it’s wrong — apostrophes don’t make plurals, and every style guide says so. But it’s also everywhere, it rarely causes genuine confusion (nobody thinks “Monday’s” on a door means “belonging to Monday”), and correcting strangers’ signage wins no friends.

The practical rule: in your own writing — CVs, emails, essays, published work — use Mondays for the plural. On a sign you walk past, let it go. Knowing the rule matters; enforcing it on shopkeepers doesn’t.

Monday in Idioms

Monday’s reputation as the week’s difficult child has stocked the language with idioms — and they all follow the standard spelling rules:

• Monday blues — the dread of the week’s start: “she had a bad case of the Monday blues.” Plural Mondays nowhere in sight; it’s the attributive Monday.
• Monday-morning quarterback (chiefly US) — someone who criticizes with hindsight: “the Monday-morning quarterbacks dissected every play.” Note the plural goes on quarterbacks, not Mondays.
• Manic Monday — the frantic start to the week, popularized as a song title; now shorthand for any chaotic Monday.
• Monday to Friday — the working week: “a Monday-to-Friday job.” Hyphenated as a compound adjective, no apostrophes, no plurals.

The pattern across all of them: Monday stays singular and capitalized when it’s modifying another noun, and the s-forms only appear for genuine plurals (Mondays) or possession (Monday’s). If an idiom needs neither, neither appears.

Correct vs. Incorrect

• ✓ “The office is closed on Mondays.” / ✗ “The office is closed on Monday’s.”
• ✓ “Monday’s weather looks perfect.” (possessive — the weather of Monday)
• ✓ “Monday’s the deadline.” (contraction — Monday is)
• ✗ “Mondays weather looks perfect.” → ✓ “Monday’s weather…” (possessive needs the apostrophe)
• ✓ “Three Mondays’ worth of meetings got postponed.” (plural possessive — rare but correct)
• ✗ “I hate mondays.” → ✓ “I hate Mondays.” (proper noun — capitalize)
• ✗ “See you Monday’s!” → ✓ “See you Monday!” / “See you on Monday!” (neither plural nor possessive — no s at all)

Common Mistakes

1. “Monday’s” for the plural. The keyword’s core question, and the most common error in the wild: “we’re closed Monday’s,” “I work Monday’s.” If you mean more than one Monday — or the recurring day as a habit — it’s Mondays, no apostrophe. Test it: would you write “apple’s” for more than one apple? Same rule.

2. “Mondays” for the possessive. The mirror image: “Mondays meeting is at ten” when you mean one Monday’s meeting. If the meeting belongs to Monday, the apostrophe is required: “Monday’s meeting.”

3. Dropping the capital. “mondays” in lowercase is wrong in standard writing — days of the week are proper nouns. Autocorrect usually catches this one; don’t fight it.

4. Overusing the plural possessive. Technically correct, but “Mondays’ meetings” is clunky enough that rephrasing is usually better: “meetings on Mondays,” “every Monday’s meetings.” Correctness isn’t the only virtue — clarity counts too.

5. Apostrophe-s on every weekday in lists. “Open Monday’s–Friday’s” doubles the error across the week. The range of days is a plural idea: “open Monday–Friday” or “open Mondays to Fridays.” No apostrophes anywhere in that construction.

Frequently Asked Questions

Is it “Mondays” or “Monday’s”?

It depends on the job: Mondays (no apostrophe) is the plural — “I work Mondays.” Monday’s (apostrophe) is the possessive — “Monday’s schedule” — or a contraction — “Monday’s (= Monday is) a holiday.” Apostrophes never form plurals.

What about “Mondays'” with the apostrophe at the end?

That’s the plural possessive: something belonging to multiple Mondays. “Those Mondays’ early alarms wore me down.” It’s correct but rare — most writers rephrase to avoid it (“the early alarms every Monday”).

Why do so many signs say “Open Monday’s”?

The greengrocer’s apostrophe: a hypercorrection so widespread it’s become a recognized phenomenon. Writers half-remember that apostrophes go with s-endings and insert one where a plain plural s belongs. It’s nonstandard in edited English but extremely common in informal signage.

Should “Monday” always be capitalized?

Yes — days of the week are proper nouns in English: Monday, Mondays, Monday’s. Always capitalized in standard writing, including the plural and possessive forms.

Does this rule apply to other days too?

Exactly the same pattern: Tuesdays/Tuesday’s, Fridays/Friday’s, Sundays/Sunday’s. Plural = bare s; possessive or contraction = apostrophe-s. Learn it once for Monday and you’ve learned it for the whole week.

The Takeaway

Mondays is the plural (“I work Mondays“). Monday’s is the possessive (“Monday’s agenda”) or a contraction (“Monday’s [= Monday is] a holiday”). Mondays’ is the plural possessive for the rare occasions you need it. The apostrophe never makes a plural — “open Monday’s” is the famous greengrocer’s error, forgivable on a shop sign, wrong in your writing. Capitalize always; apostrophize only for possession or contraction.