How major style guides rule on "set up (verb) / setup (noun)"
Verb is two words, noun is closed. Confusion with 'setup' as a verb is among the most common style errors in technical writing.
The disagreement on "set up (verb) / setup (noun)" is an example of phrasal verbs (open) vs derived nouns (closed), the category of style-guide differences that most often confuses copy editors and creates inconsistency across long documents. Below is a guide-by-guide breakdown, drawn directly from the published editions cited.
| Style guide | Preferred form |
|---|---|
| AP Stylebook (2024–2025 Edition) | set up (v.), setup (n.) |
| Chicago Manual of Style | set up (v.), setup (n.) |
| MLA Handbook | set up (v.), setup (n.) |
| APA Publication Manual | set up (v.), setup (n.) |
| Merriam-Webster Dictionary | set up (v.), setup (n.) |
What the divergence actually means
Unlike many compound-modernization decisions where style guides eventually converge, "set up (verb) / setup (noun)" continues to show genuine divergence between major guides. The AP Stylebook treats this as a settled call; Chicago Manual leaves more flexibility; and Merriam-Webster, as a descriptive dictionary, records both forms. Source: Chicago Manual of Style, 17th Edition
The APA Publication Manual aligns with AP and Chicago on "set up (verb) / setup (noun)", though APA generally addresses spelling questions only when they intersect with statistical reporting or technical psychology vocabulary. Where the manual is silent, APA defers to Merriam-Webster as its standard reference. Source: APA Publication Manual, 7th Edition
Merriam-Webster lists "set up (v.), setup (n.)", which serves as the lexicographic baseline for U.S. style decisions. Because Merriam-Webster's entries reflect aggregated published usage rather than editorial preference, when a guide says "follow Merriam-Webster", as APA does, that effectively delegates the call to whichever spelling has dominated the published corpus. Source: Merriam-Webster Dictionary
Garner's Modern English Usage classifies the "set up (v.) / setup (n.)" / "setup (verb)" pair on its Language-Change Index, a five-stage scale measuring whether a once-disputed form has been accepted into Standard English. For phrasal verbs (open) vs derived nouns (closed), Garner's typically rates the dominant form at Stage 4 ("ubiquitous but objected to by traditionalists") or Stage 5 ("fully accepted"). Source: Garner's Modern English Usage, 5th Edition
Practical guidance for editors
For working writers, the practical rule is straightforward: in journalism, follow AP; in academic writing in the humanities, follow MLA or Chicago; in social-science publishing, follow APA; in book publishing, follow Chicago. When no house style applies, Merriam-Webster's main entry is the safest default. The differences across these guides on "set up (verb) / setup (noun)" reflect not disagreement about correctness but different audiences and editorial pressures.
Editorial context
In computing and software documentation, the closed form setup thrives as a verb despite formal style guides' insistence on the phrasal set up, reflecting a pragmatic shift toward brevity in technical registers. Installation wizards and manuals from the 1990s onward routinely instruct users to setup your printer or setup the server, as evidenced in early Microsoft and Adobe guides where the noun-verb merger streamlined commands amid rapid industry growth. This usage, peaking in specialized corpora like the Corpus of Contemporary American English's tech subdomain by the early 2000s, prioritizes efficiency over traditional distinctions, often treating setup as a back-formation from the noun. Copy editors encountering such material frequently default to the closed verb, perpetuating the error outside tech contexts, since general corpora still favor set up for clarity in broader prose.
Cross-references
For the dictionary entry, frequency data, and pronunciation of set, see the main word page. For other style-guide spelling decisions in this category, browse all style-guide spelling rulings.