The short answer is that the correct way to spell the phrase is ‘each other.’ The words require a space between them because they’re two separate words, unlike phrases like everyday, which can be used both together or apart (and they mean somewhat different things).

However, the correct spelling and usage is ‘each other’—two separate words—particularly in formal writing and professional or educational settings.

The rule for using ‘each other’ and ‘one another’ correctly is to use ‘each other’ when referring to two people or things and ‘one another’ when referring to three or more people or things.

We write each other as two separate words and we do not use a hyphen (-): We got to know each other very quickly. Not: We got to know eachother We don’t use each other or one another as a plural form: They love each other. Not: They love each others.

Just remember: If each is plural, it is each others’, but if it is not (singular), it is talking about one person, so it would be this: “each other”.