When you type a farewell and pause over the spelling, you're not alone. The question of good by vs good bye vs goodby vs goodbye trips up writers of all levels, because all four forms have existed in print at some point in English history. Only one is correct in modern standard writing. That form is goodbye, one word, no space, no hyphen.
The correct spelling is goodbye
Goodbye is the only form that appears in major dictionaries, including Merriam-Webster and the Oxford English Dictionary, as the standard spelling. It functions as a noun, an interjection, and occasionally an adjective. You say goodbye to someone, bid them a goodbye, or wave a goodbye from the doorstep. Every use takes the same single-word form.
The variants, good by, good bye, and goodby, are either archaic or misspellings. They don't appear as accepted entries in current reference works. If you write "good bye" with a space, a careful editor will close it. "Goodby" without the final e is an occasional older American spelling that has since been standardised out of use. "Good by" as two words never had strong dictionary backing.
Where goodbye actually comes from
Goodbye is a contraction. It started as the phrase "God be with ye," a parting blessing that English speakers used from at least the 16th century. Over generations, rapid speech compressed those five syllables. "God be with ye" became "godbwye," then "goodbye," with the first element shifting from "God" to "good" under the influence of parallel phrases like "good day," "good night," and "good morning."
That shift explains why "good" appears at all. It was a kind of linguistic gravity: so many polite farewells started with "good" that the word pulled "goodbye" into the same pattern. The result is a word that looks like it means something positive, but is actually a compressed prayer of safe passage.
The two-word form "good bye" was common in 18th and 19th century print, which is why it still feels plausible to modern writers who've encountered it in older texts. It's the same process that produces misspellings like afterall instead of after all: the historical record makes the wrong form look familiar.
How to remember it
Think of goodbye the same way you think of other compound farewell words: goodnight, goodbye, goodwill. All one word. English collapses common pairings over time, and goodbye completed that process a long time ago. If you're still unsure, notice that "good morning" and "good afternoon" remain two words, while "goodbye" and "goodnight" merged. The difference is frequency and convention, not any logical rule you can predict. Just memorise the closed forms: goodnight and goodbye.
A useful check: if you're tempted to write "good bye" or "good by," ask whether you would write "good night" as one or two words in a formal context. You'd probably leave "good night" as two words, but you'd close "goodbye." That instinct is correct. Hold onto it.
Spelling instincts can go wrong in exactly this way across English. Compare the confusion around judgement vs judgment, where historical variation in print still makes writers second-guess a form that has settled into a clear standard.
Is "goodbye" ever spelled differently in acceptable usage?
There is one minor variation worth knowing: good-bye, hyphenated. This form appears in some older dictionaries and American English texts from the early 20th century. It isn't wrong in the strictest sense, but it reads as old-fashioned now. Modern style guides and publishing standards prefer the unhyphenated goodbye. Unless you're deliberately imitating a historical style, skip the hyphen.
The plural is goodbyes, not goodbyes' or goodbye's. You can say "she said her goodbyes" without any punctuation complication. As a modifier, goodbye works fine: "a goodbye hug," "the goodbye wave." No hyphen needed in those compounds either.
Quick reference
- Goodbye: correct. Use this in all modern writing.
- Good-bye: old-fashioned but not strictly wrong. Avoid in modern contexts.
- Goodby: archaic American variant. Not accepted in current standard English.
- Good bye: misspelling. Two words with a space is not standard.
- Good by: misspelling. Never had firm dictionary support.
The answer is simpler than the history suggests. Write goodbye, close it up, drop the hyphen, and move on. The word has been settled for well over a century.