If you've ever typed "eachother" and felt a flicker of doubt, you're not alone. The question of whether it's eachother or each other comes up constantly in professional writing, and the answer is firm: each other is always two words. There is no one-word form in standard English, and no style guide accepts "eachother" as a valid spelling.
Why writers run the two words together
The confusion is understandable. Words that appear side by side constantly often fuse over time. "Every day" and "everyday" are a well-known example of that process mid-journey. But "each other" hasn't followed that path. Dictionaries on both sides of the Atlantic, including Merriam-Webster, list it exclusively as two words. The fused form "eachother" appears in no major dictionary and reads as a typo to anyone editing professional documents.
Part of the issue is speed. When you're composing an email quickly, the two words can blur together on the screen, and autocorrect doesn't always catch the error. It's the same muscle-memory trap that produces "alot" instead of "a lot."
How "each other" works grammatically
"Each other" is a reciprocal pronoun. It refers to a mutual action or relationship between two or more people (or things). Both words carry distinct grammatical weight, which is exactly why they stay separate.
- Each distributes the action individually to every member of the group.
- Other points that action outward, toward the rest of the group.
Strip either word out and the sentence collapses. They aren't a compound noun or a fused idiom. They're two words doing two jobs.
Here's what correct use looks like in practice:
- The two departments need to trust each other more.
- They emailed each other three times before agreeing on the date.
- Team members should support each other during high-pressure deadlines.
Each other vs one another
A closely related question is whether to use "each other" or "one another." Traditional grammar held that "each other" referred to exactly two parties, while "one another" applied to three or more. That distinction has largely softened in modern usage. Most style guides now treat the two as interchangeable in everyday writing.
If your organisation follows a strict house style, check whether it specifies a preference. In most business writing, "each other" is the safer and more natural-sounding choice regardless of group size.
Possessive form: "each other's"
When you need the possessive, add an apostrophe and an s to the second word only: each other's. The apostrophe goes on "other," not on "each."
Correct: They read each other's drafts before submitting the report.
Incorrect: They read each others' drafts before submitting the report.
This trips writers up because the possessive feels like it should land on "each," the first word. It doesn't. The apostrophe rule here follows the same logic as any other possessive: it attaches to the word that directly precedes the thing being owned, which in this construction is "other." For more on how apostrophes work in tricky situations, the post on more apostrophe rules you need to get right covers the full range of cases that catch professional writers off guard.
Quick test for your own writing
Before you finalise any document, run a simple search for "eachother" as a single string. Most word processors won't flag it automatically because it isn't a recognised misspelling in many default dictionaries. It will just sit there. A manual search takes three seconds and catches the error every time.
The same logic applies to similarly fused errors. If you're in the habit of confusing homophones or near-homophones in fast drafts, the article on led or lead shows how small spelling differences can quietly undermine an otherwise professional document.
The bottom line
"Each other" is two words. It has always been two words. It will remain two words in every professional context you encounter. The fused form "eachother" is a typo, not a variant. Write it as two words, add the apostrophe to "other's" when you need the possessive, and move on.