missing hyphen in 'three line'

Hyphens join words that act together to modify a noun and prevent misreading. Hyphenate compound modifiers that come before a noun (a three-line form); don't hyphenate the same words after the noun (the form is three lines). Use short tests below to decide quickly.

Quick answer

Hyphenate compound modifiers before a noun: a three-line notebook, a five-year plan. Don't hyphenate when the phrase follows the noun or when an -ly adverb modifies an adjective: highly regarded.

Before a noun → hyphenate: three-line notebook, long-term project.
After a noun (predicate) → no hyphen: The notebook is three lines.
-ly adverb + adjective → no hyphen: highly regarded scientist.

Core hyphenation rule

If two or more words act together to describe a noun and appear before it, join them with a hyphen so the reader sees one idea. If the same words come after the noun, don't hyphenate. When in doubt for professional writing, choose the hyphen to preserve clarity.

Premodifier (before noun) → hyphenate.
Predicate (after noun) → don't hyphenate.
When clarity suffers, add the hyphen.

Wrong: She has a three line notebook. /
Right: She has a three-line notebook.
Wrong: He is on a long term assignment. /
Right: He is on a long-term assignment.

Number + unit compounds (three-line, five-year, two-story)

When a number and a unit jointly describe a noun and appear before it, use a hyphen-whether the number is spelled out or numeric. If the phrase follows the noun, don't hyphenate.

Before noun: five-year plan, two-story house, three-line worksheet → hyphenate.
After noun: The plan lasts five years; The house is two stories tall → no hyphen.

Wrong: They approved a ten year plan. /
Right: They approved a ten-year plan.
Wrong: I need a five year plan. /
Right: I need a five-year plan.
Wrong: They live in a two story home. /
Right: They live in a two-story home.

Prefixes and fixed compounds (well-known, re-elect, anti-inflammatory)

Use a hyphen when a prefix prevents misreading, creates awkward double letters, or attaches to a proper noun (re-elect, anti-inflammatory, pro-American). Many compounds have become closed (email, nonprofit); follow your style guide for consistency.

Hyphenate to avoid confusion or odd letter clusters: re-elect, re-enter, anti-inflammatory.
Fixed compound adjectives before nouns are usually hyphenated: a well-known actor; after the noun they often aren't: The actor is well known.

Wrong: She is a well known author. /
Right: She is a well-known author.
Wrong: The board will re elect the chair. /
Right: The board will re-elect the chair.
Usage (school): Use anti-inflammatory in lab reports when naming the drug class.

Hyphen vs en dash vs em dash and spacing

Use a hyphen (-) to join words. Use an en dash (-) for ranges or connections and an em dash (-) for a break in thought. Hyphens have no spaces; dashes follow your style guide on spacing.

Hyphen (no spaces): three-line notebook.
En dash for ranges or connections: pages 10-12, New York-London flight.
Em dash for interruptions or emphasis-the spacing varies by style.

Wrong: Johnson-&-Johnson. /
Right: Johnson & Johnson.
Wrong: pages 10-12 (typed hyphen). Better: pages 10-12 (en dash) or pages 10 to 12.

Try your own sentence

Test the full sentence, not just the phrase. Context usually makes the right choice clear-then apply the swap and -ly tests below.

Grammar edge cases: -ly adverbs and predicate adjectives

-ly adverbs don't form hyphenated compounds with adjectives: highly regarded, deeply rooted, closely held. Also, compounds used after the noun generally lose the hyphen.

Don't hyphenate an -ly adverb + adjective.
Hyphenate premodifiers; don't hyphenate the same words in predicate position.

Wrong: She is a highly-regarded scientist. /
Right: She is a highly regarded scientist.
School: a long-term study (before noun) vs the study was long term (after noun).

Real usage: workplace, school, and casual examples

Match your strictness to context. Use hyphens consistently in professional and academic writing; casual writing can be looser if meaning stays clear. Below are ready examples you can copy.

Work: Please review the three-line summary before the meeting.
Work: The five-year forecast needs sign-off by Friday.
Work: Send the two-page memo to the team.
School: Turn in a three-line answer on the worksheet.
School: Submit a ten-page literature review (ten-page as a premodifier).
School: The experiment lasted five minutes (no hyphen in predicate).
Casual: I bought a three-seater couch for the apartment.
Casual: We had a two-hour drive-no stopping.
Casual: That high school reunion was fun (high school as a compound noun; no hyphen in common US usage).

Step-by-step: how to fix your sentence (rewrites you can paste)

Three quick edits: 1) Move the phrase after the noun to see if the meaning still works; 2) If an -ly adverb is present, remove any hyphen; 3) If confusion remains, rephrase.

Swap the phrase after the noun to test for hyphenation.
If an -ly adverb is present, don't hyphenate.
When ambiguity remains, rewrite the clause.

Rewrite:
Original: I filled out a three line form. /
Rewrite: I filled out a three-line form.
Rewrite:
Original: They created a long term strategy. /
Rewrite: They created a long-term strategy.
Rewrite:
Original: The study was ten years long. /
Rewrite: The ten-year study was published last month.

Memory trick

Use three short tests whenever you hesitate.

Swap test: move the phrase after the noun-if that reads naturally, hyphenate when it's before the noun.
-ly test: if the first word ends in -ly, don't hyphenate.
Single-idea test: read the modifier as one idea-if it must be read together, hyphenate before the noun.

Similar mistakes and quick checks

Watch closed compounds and dash confusions. A hyphen can change the word class: break-even (adjective) vs break even (verb). When in doubt, apply the swap and -ly tests or rephrase.

break-even (adjective) vs the company will break even (verb).
email (common) vs e-mail (older style) - follow your style guide.
If adding a hyphen removes ambiguity, prefer the hyphen in professional writing.

Wrong: Please email-me the file. /
Right: Please email me the file.
Wrong: They approved a ten year plan. /
Right: They approved a ten-year plan.
Wrong: Johnson-&-Johnson. /
Right: Johnson & Johnson.

FAQ

Do I need a hyphen in 'three-line'?

Yes when it appears before a noun as a compound adjective (a three-line form). If the phrase follows the noun (the form is three lines), don't hyphenate.

Should numbers be hyphenated (e.g., five year plan)?

Hyphenate number+unit compounds before a noun: five-year plan, two-story building. Don't hyphenate when the phrase follows the noun (the plan lasts five years).

When do I use hyphens with prefixes like re- or anti-?

Use hyphens when the prefix would cause confusion or awkward double letters (re-elect, re-enter) or when attaching to a proper noun. Many modern compounds are closed; follow your style guide.

Is 'highly-regarded' correct?

No. Adverbs ending in -ly don't take hyphens with the adjective they modify. Write highly regarded without a hyphen.

How can I quickly check my sentence for the right hyphenation?

Swap the modifier after the noun; check for -ly; and read the modifier as a single idea. If ambiguity remains, rephrase for clarity.

Need a quick check?

Use the swap test and the -ly test as a first pass. For fast, context-aware suggestions, paste your sentence into a grammar tool that flags hyphen issues and suggests rewrites tailored to your audience.