into / in to: Style Guide Spelling Decisions (AP, Chicago, MLA, APA)

How major style guides rule on "into / in to"

'Into' shows direction or transformation; 'in to' is the adverb 'in' followed by the preposition 'to' ('she turned in to the police').

The disagreement on "into / in to" is an example of compound preposition vs separated adverb-plus-preposition, 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.

What the divergence actually means

Unlike many compound-modernization decisions where style guides eventually converge, "into / in to" 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 "into / in to", 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 "context-dependent", 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 "into (preposition) / in to (adverb + preposition)" / "into (always)" pair on its Language-Change Index, a five-stage scale measuring whether a once-disputed form has been accepted into Standard English. For compound preposition vs separated adverb-plus-preposition, 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 "into / in to" reflect not disagreement about correctness but different audiences and editorial pressures.

Editorial context

Copy editors most often err on into versus in to by failing to detect when in acts adverbially with verbs of motion or submission, defaulting to the fused preposition out of familiarity with dominant uses. A telltale mistake occurs in revising He pulled the car in to the curb, where many change it to into despite pull in forming a separable phrasal verb synonymous with park, with to the curb as its directional complement. This misstep stems from print traditions emphasizing fusion for smoothness, as noted in editorials from the 1940s Chicago Tribune style memos, compounded by autocorrect software that rarely distinguishes. Even though corpora like the British National Corpus show in to comprising 15-20% of relevant instances since the 1990s, hurried desk work prioritizes into's visual unity. Training via examples from Garner's Modern English Usage (4th ed., 2016, p. 458) reinforces the split, yet the error endures in galleys across newsrooms, highlighting the adverb test's counterintuitive application in real-time editing.

Cross-references

For the dictionary entry, frequency data, and pronunciation of into, see the main word page. For other style-guide spelling decisions in this category, browse all style-guide spelling rulings.