Terms and Style

3.1Words and Their Forms

Use consistent wording so readers can follow your meaning. This is especially helpful when similar words have different roles or when a phrase has a specific meaning in your piece.

3.1.1Compounds and Prefixes

A compound brings two or more words together to express one idea. Its spelling may be open, closed, or hyphenated. The form is not a measure of how closely the ideas belong together; it is usually a matter of established usage.

• Open compounds keep their spaces: ice cream, post office, and living room.
• Closed compounds are written as one word: notebook, sunflower, and bookshelf.
• Hyphenated compounds connect their parts with hyphens: mother-in-law and runner-up.

Check a dictionary for your variety of English when a spelling is unfamiliar. Similar-looking words do not always follow the same pattern, and dictionaries may record more than one form. Keep a consistent spelling for the same meaning within a piece.

A word’s role can also change its form. Setup is a noun or adjective; set up is a verb. That distinction is about how the words work in the sentence, not simply whether you prefer a space.

Different roles: The setup was simple. We set up the table beside the window.

See Compound Modifiers for words that work together to describe a noun, and Prefixes for beginnings such as re-, pre-, and non-. Hyphens and En Dash explain how the punctuation works.

3.1.1.1Compound Modifiers

A compound modifier is a group of words that describes a noun as a unit. A hyphen often makes the grouping clearer before the noun, especially when a reader could otherwise attach the words differently.

Before the noun: We took a five-minute walk.

A useful distinction: A small-business owner owns a small business. A small business owner could be read as an owner who is small.

Many temporary modifiers lose their hyphens when they follow the noun. That is a useful pattern, not a rule for every compound. Established forms may keep their hyphens, so check the dictionary when you are unsure.

Before and after: The bread has a well-baked crust. The crust is well baked.

Do not add a hyphen between an adverb ending in -ly and the adjective or participle it modifies. Very also stays separate.

No hyphen: a carefully written letter; a very thoughtful reply

Not every pair of words before a noun needs a hyphen. Familiar, unambiguous phrases such as ice cream shop can stay open. A proper name keeps its own spaces: New Balance sneakers.

When an open phrase connects to another word in a larger modifier, an en dash can show the grouping: a New York–based writer. Two already-hyphenated groups can also be joined by an en dash: a trade-in–trade-up program. See En Dash for the full explanation.

When two modifiers share an ending, a suspended hyphen can stand in for the omitted part. Keep the hyphen before the space, or repeat the full wording if that reads more easily.

A shared ending: five- and ten-minute walks

Spelled out: five-minute and ten-minute walks

The punctuation should make the meaning easier to follow. If the modifier becomes a maze, put the idea into a phrase or another sentence.

Two adjectives can also describe a noun separately, as in a warm, sunny afternoon. See Commas for the difference between independent descriptions and words that form one modifier.

3.1.1.2Prefixes

A prefix adds meaning to the beginning of a word. Many familiar combinations are written without a hyphen: reread, preview, and nonfiction. Follow established spellings rather than adding a hyphen to every prefix.

A hyphen can prevent a misreading or separate a prefix from a proper name or numeral.

A different meaning: Re-sign the letter if the signature is missing. Resign from the role if you intend to leave it.

A name or numeral: anti-American; pre-2020

When the prefix applies to a whole open compound, this guide uses an en dash: pre–World War II. When it attaches to an already-hyphenated compound, another hyphen usually does the job: non-English-speaking.

Spellings vary across Englishes and change over time. Use a dictionary that suits your writing, record recurring choices, and rewrite an awkward construction when that helps the reader.

3.1.2Putting Words in Order

Use letter-by-letter alphabetization for a word list or glossary. Ignore spaces, hyphens, and apostrophes when comparing letters.

Example: Art, artist, artist’s notebook, arts festival.

Alphabetize abbreviations as written. Group entries that begin with numerals before A–Z entries and choose a consistent order within that group. Retain symbols when they change a technical term’s meaning.

3.2Abbreviations and Acronyms

An abbreviation is a shortened form of a word or phrase. An acronym is an abbreviation pronounced as a word, such as NASA. An initialism is read letter by letter, such as DIY.

Short forms save space, but only when readers understand them. Start with common examples and open the specialist lists if you need them.

See also Abbreviations, Acronyms, and Initialisms.

3.2.1Everyday Abbreviations

DIY

do it yourself

ETA

estimated time of arrival

FAQ

frequently asked question

P.S.

postscript

RSVP

a request to reply to an invitation

TBA

to be announced

TBD

to be determined

Use these when they are familiar to your readers. Spell them out or use a direct phrase when an abbreviation would add work.

3.2.3When To Spell It Out

Ask whether the short form makes the sentence easier to read. A space-saving label can become an obstacle if readers must stop and decode it.

Example: Please reply by Friday.

That may be all you need instead of a formal abbreviation. When a term recurs and its short form is useful, define it once and use it consistently.

3.3Word List

The A–Z word list is a place to untangle similar words, check a spelling, or find the form you need. Everyday writing comes first; digital terms and names have their own collections.

For a word you don’t find here, try a dictionary that reflects your variety of English.

3.3.1Numbers and Symbols

Entries beginning with numbers appear in the # group of the word list.

3.3.2A–Z

Browse the word list by letter, or search for a term.