guest edit (guest-edit)

Short verdict: Don't add spaces around hyphens that join parts of a single word or a compound modifier. Use an en dash (-) for ranges and connections, and an em dash (-) for interruptions; whether em dashes get spaces depends on house style.

Quick verdict

Hyphens bind (no spaces). En dashes connect or show ranges. Em dashes break or emphasize; spacing varies by style.

Hyphen: tight, no spaces - co-worker, well-known, twenty-one.
En dash (-): ranges/connections - 2019-2020, New York-London.
Em dash (-): interruptions/emphasis - He left-surprisingly-early. (Style determines spaces.)

Core hyphen rules (no spaces)

Use a hyphen to join parts of one grammatical unit: prefixes, compound modifiers before a noun, and some set compounds. If you see spaces around a short dash, remove them or replace the character with an en or em dash if the meaning calls for it.

Join prefixes and compounds: co-founder, pre-existing, self-esteem.
Compound modifier before a noun: a well-known author, a 30-year-old student.
No hyphen when the modifier follows the noun: The author is well known.

Wrong: co - founder
Right: co-founder
Wrong: self - esteem
Right: self-esteem
Wrong: open - source project
Right: open-source project

Hyphen vs en dash vs em dash: purpose and spacing

First choose the intent: join (hyphen), connect/range (en dash), or break/interrupt (em dash). Use the proper dash character for clarity and correct typography.

Hyphen (-): ties parts of one word or a compound modifier: user-friendly.
En dash (-): shows ranges or links: 2019-2020, New York-London (no spaces).
Em dash (-): marks interruptions/emphasis: He paused-then left. (Chicago: no spaces; AP: spaces.)

Wrong: 2019 - 2020
Right: 2019-2020 (en dash preferred)
Wrong: New York - London flight
Right: New York-London flight
Wrong: The plan - if approved - starts next week.
Right (Chicago): The plan-if approved-starts next week.

Hyphenation rules for numbers, ages, and fractions

Hyphenate numeric compounds when they modify a noun. When the age or number follows the noun, write the elements open.

Before a noun: a 20-year-old student (hyphen).
After the noun: The student is 20 years old (no hyphen).
Fractions as adjectives: a two-thirds majority (hyphenated).
Spelled-out compound numbers: twenty-one to ninety-nine (hyphenate).

School - Wrong: He is a 20 year old student.
School - Right: He is a 20-year-old student.
School - Wrong: a two thirds majority
School - Right: a two-thirds majority
School - Wrong: twenty one students
School - Right: twenty-one students

Spacing and punctuation around hyphens

Hyphens stay attached to the words they join. Punctuation like commas and periods comes after the whole compound unless a grammatical rule requires otherwise. If you see spaces around a short dash, check whether the writer meant a dash (en/em) or accidentally separated a hyphen.

No spaces: save-the-date, mother-in-law, state-of-the-art.
Commas/periods follow the whole compound: I invited the well-known author, but she declined.
End of sentence: He is a 30-year-old.

Casual - Wrong: save - the - date
Casual - Right: save-the-date
Wrong: a well - known author,
Right: a well-known author,
Wrong: She is a 30 - year - old.
Right: She is a 30-year-old.

Try your own sentence

Test the whole sentence, not the isolated phrase. Context usually makes the correct punctuation clear.

Real-world examples: work, school, casual

Quick rewrites to apply in reports, essays, and messages: remove spaces around hyphens that join words, hyphenate compound modifiers before nouns, and use en dashes for ranges.

Work: prefer clarity in headings and modifiers (year-end, long-term).
School: hyphenate compound adjectives before nouns for grading clarity (two-week project).
Casual: keep familiar compounds hyphenated (mother-in-law, part-time).

Work - Wrong: year - end report
Work - Right: year-end report
Work - Wrong: sales - meeting
Work - Right: sales meeting
Work - Wrong: co - worker feedback
Work - Right: co-worker feedback
School - Wrong: long term effect
School - Right: long-term effect
School - Wrong: two week project
School - Right: two-week project
School - Wrong: well known author
School - Right: well-known author
Casual - Wrong: mother in law
Casual - Right: mother-in-law
Casual - Wrong: part time job
Casual - Right: part-time job
Casual - Wrong: run of the mill tune
Casual - Right: run-of-the-mill tune

Rewrite help: a three-step checklist + quick rewrites

Checklist: 1) Function: do the words act as one idea before a noun? 2) Character: hyphen (-), en dash (-), or em dash (-)? 3) Rephrase: move the modifier after the noun if unsure.

Step 1: Identify whether the words act together as one adjective before a noun.
Step 2: Choose the correct dash character for meaning.
Step 3: Move the phrase after the noun if that removes ambiguity.

Rewrite: The team made a long term plan. → The team made a long-term plan.
Rewrite: Install the user friendly interface. → Install the user-friendly interface.
Rewrite: She is a 30 year old chef. → She is a 30-year-old chef.
Rewrite: This affects the 2019 - 2020 budget. → This affects the 2019-2020 budget.
Rewrite: I need a break - I'll be back. → I need a break-I'll be back. (or: I need a break; I'll be back.)
Rewrite: We hired a state of the art team. → We hired a state-of-the-art team.

Common similar mistakes (dashes, spaces, apostrophes, slashes)

People often confuse hyphens with en/em dashes, add spaces around short dashes, or misuse apostrophes and slashes. Small punctuation errors change meaning and tone.

Fix these by picking the right character and removing unintended spaces.

Wrong dash choice: use an en dash for ranges and an em dash for breaks; don't rely on a hyphen when typography matters.
Apostrophe mistakes: 1990's (wrong for plural) → 1990s (right).
Slash spacing: use and/or (no spaces) in formal text.

Wrong: 1990's sales
Right: 1990s sales
Wrong: and / or
Right: and/or
Wrong: 2020 - 2021 results
Right: 2020-2021 results

Memory tricks and a quick editorial note

Mnemonic: "Before a noun? Bind with a hyphen." If two or more words jointly modify a following noun, hyphenate them; if they follow the noun, leave them open. Consistency beats perfection-pick a house style and stick to it.

Test: can you insert "very" between the words? If yes, don't hyphenate (very long ≠ long-term).
Record choices for recurring terms (email vs e-mail, coworker vs co-worker) in a mini style sheet.
When typography matters (books, PDFs), use true en (-) and em (-) dash characters.

FAQ

Should there be a space before a hyphen?

No. A hyphen that joins parts of a compound word or modifier should have no spaces. If you see spaces, remove them or check whether an en or em dash was intended.

When do you hyphenate compound adjectives?

Hyphenate compound adjectives that appear before the noun they modify (a long-term study). If the phrase follows the noun, it usually remains open (the study was long term).

En dash or hyphen for date ranges?

Use an en dash for ranges: 2019-2020. It's typographically correct and clearer than a simple hyphen.

How do I type en and em dashes?

Mac: en dash = Option + hyphen, em dash = Shift + Option + hyphen. Windows: use Alt codes (Alt+0150 en dash, Alt+0151 em dash) or insert the symbol in your editor.

Should I hyphenate ages like "20-year-old"?

Yes-hyphenate ages when they function as modifiers before a noun (a 20-year-old student). If the age follows the noun, write "The student is 20 years old."

Want to check a sentence quickly?

Paste a sentence into a grammar checker to get an immediate suggestion and a short explanation-whether you need a hyphen, an en dash, or an em dash. Use the feedback to learn the pattern for next time.