Formerly vs. formally: spotting the difference in writing

The short answer

Formerly means previously or at an earlier time, describing something that used to be true but no longer is. Formally means in a proper, official, or ceremonious manner, describing how something is done rather than when it happened. The two words differ by a single letter, which is why they are so often swapped by accident.

Reading the sentence and asking whether it describes a past state or a proper manner will usually reveal which spelling belongs there, even when the surrounding sentence looks fairly formal either way, and even when both words seem plausible at first glance.

What each word means

Formerly is an adverb built from the word former, meaning past or previous, as in the building was formerly a train station before it closed decades ago. It signals a change from an earlier status to a current one, often used to introduce a person's or a place's past identity or name to a reader.

Formally is an adverb built from the word formal, meaning proper, official, or done according to established rules, as in the committee formally approved the budget after months of debate. It describes the manner of an action, such as speaking, dressing, or announcing something, rather than describing a point in time.

Why they get mixed up

Formerly and formally differ by only one letter and share the same first six letters, so a quick typo or a fast read easily swaps one for the other without anyone noticing right away. Because both words also appear in similarly formal contexts, such as business writing or news reports, the visual similarity compounds the everyday confusion.

Correct and incorrect examples

Use formerly for a past state and formally for a proper manner, and check each sentence against that rule before publishing it. Correct: the company was formerly known as Acme Tools. Not: the company was formally known as Acme Tools, unless it truly held an official renaming ceremony. Correct: the mayor formally opened the new library. Not: the mayor formerly opened the new library.

• Correct: She formerly worked as a nurse.
• Correct: They were formally introduced at the gala.
• Not: They were formerly introduced at the gala.
• Correct: The road was formerly a footpath.

A useful substitution test

Before publishing a sentence, swap in previously for the word in question. If the sentence still makes sense, formerly is correct. Next, try swapping in officially or properly instead. If that version makes sense, formally is the word you need, and this quick two-step check resolves nearly every case a writer will encounter.

This test works especially well in professional writing, such as press releases or biographies, where both words tend to appear more often than in casual conversation between friends, and where getting the choice wrong is more likely to be noticed by a careful reader.

Remember it

Link formerly with former, since both describe something in the past, and link formally with formal, since both describe proper or official manner. If you can replace the word with previously, formerly is correct; if you can replace it with officially, formally is the word you need in that sentence.