I'm specifically talking about British English. In British English, "bath" (noun) has a long vowel ([ɑː]) while the verb "bathe" has a diphthong ([]) and sounds more like the American version of "bath".

Etymonline on "bath" says:

"bath (n.) Old English bæð "an immersing of the body in water, mud, etc.," also "a quantity of water, etc., for bathing," from Proto-Germanic *badan (source also of Old Frisian beth, Old Saxon bath, Old Norse bað, Middle Dutch bat, German Bad), from PIE root *bhē- "to warm" + *-thuz, Germanic suffix indicating "act, process, condition" (as in birth, death). The etymological sense is of heating, not immersing."

And on "bathe":

"bathe (v.) Old English baþian "to wash, lave, place in a bath, take a bath" (transitive and intransitive), from root of bath (q.v.), with different vowel sound due to i-mutation. Related: Bathed; bathing. Similar nouns in Old Norse baða, Old High German badon, German baden."

However it doesn't say anything about why "bath" has a long a vowel /bɑːθ/ and "bathe" has a vowel like American "bath" /bð/. Googling didn't help much. I also read different articles (like grammarly) but to no avail.

There is also a question in this platform but that does not explain this difference: "to bath" vs "to bathe"

Does anyone know the reason they are pronounced differently?

EDIT after the two answers:

I did not know the symbols that are used to represent the vowel sounds so I confused them.

I should not have compared the vowels in American "bath" and British "bathe". Also pointed out by the commenters.

  • Comments are not for extended discussion; this conversation has been moved to chat. – tchrist Aug 23 at 20:41

I assume you're talking about Southern British English. Because 'bath' in Northern British English is pronounced /bæθ/, not /bɑ:θ/.
In Southern British English, 'bath' is pronounced /bɑ:θ/ and 'bathe' is pronounced /beɪð/.

I don't know what happened to these words in Old and Middle English but I'm going to apply some general pronuncation rules (Modern English).

The pronuncation of 'bath' was originally /bæθ/ in the South but due to a split known as trap bath split, the short vowel [æ] shifted to the long vowel [ɑː] before some consonants (/θ/, /sk/, /st/, /ft/ etc).


  • Ask: /æsk/ in the North and /ɑ:sk/ in the South.
  • Draft: /dræft/ in the North and /drɑ:ft/ in the South.
  • Fast: /fæst/ in the North and /fɑ:st/ in the South.
  • Bath: /bæθ/ in the North and /bɑːθ/ in the South.

According to Pronunciation Studio:

The split is found in many very common words like: GLASS, CAST, ENHANCE and PATH. It only happens in words that are spelt with an ‘a’ which appears before one of the following consonant sounds or clusters:

+/n(t)ʃ/ BRANCH, RANCH
+/sk/ TASK, MASK

The split appeared in southern English pronunciation in the mid-17th century and it’s not clear why it affected some words and not others, though there is a clear tendency for it to appear in shorter and more commonly used words.

When we add the silent e to a word, it usually changes the vowel in a word to a diphthong or a long vowel.


  • Mat /mæt/ -> mate /meɪt/
  • Rat /ræt/ -> rate /reɪt/
  • Bit /bɪt/ -> bite /baɪt/ etc.

The /æ/ vowel seems to have a special relationship with /eɪ/.

When a word has the /æ/ vowel and we add the silent e to it, the /æ/ vowel often changes to /eɪ/.

This relationship can also be seen in words like profane and profanity.

The silent e often indicates a long vowel or a diphthong.

So the pronunciation of 'bath' was /bæθ/ and the silent e at the end of 'bathe' indicates that it has either a long vowel or a diphthong.

The Wikipedia article on silent e has also mentioned it:

Digraphs are sometimes treated as single letters for purposes of this rule:

bath, bathe (/bæθ/, /beɪð/)
breath, breathe (/bɹɛθ/, /bɹið/)
cloth, clothe (/klɔθ/, /kloʊð/)

The trap bath split did not affect 'bathe' so its pronuncation remained unaffected (i.e. /beɪð/).

It's worth noting that the vowel in 'bathe' is not the vowel in American English 'bath' as pointed out by Peter Shor in his comment.

The [ð] in 'bathe' is because of intervocalic fricative voicing.

| improve this answer | |
  • 1
    So... I'm an AmE speaker, but it seems from this answer as though "bathe" is pronounced the same in BrE and AmE: /beɪð/ Maybe instead of comparing the vowel in BrE 'bathe' to the vowel in AmE 'bath', we could compare the vowel in BrE 'bathe' to the vowel in AmE 'bathe'. Or instead of "instead," maybe "in addition to." – shoover Aug 21 at 20:43
  • 2
    @shoover, You're absolutely right. I'm not comparing AmE 'bath' and BrE 'bathe', it was the OP who compared them. 'Bathe' has the same pronunciation in both GenAmEn and SSBrEn. – Decapitated Soul Aug 21 at 20:46

bathe: the a was lengthened in Middle English, which results in the Modern English "face" vowel [eɪ]

“Bathe” is pronounced with [eɪ] (which is not the sound in the American version of "bath") because [eɪ] is what a Middle English long [aː] sound turned into. The vowel in the verb bathe was lengthened during the Middle English period because the verb originally had a vowel after the ”th” consonant sound: when this vowel sound was lost (or before it was lost), it caused lengthening of the [a] in the preceding syllable. The same kind of vowel alternation shows up in the noun/verb pairs grass/graze and glass/glaze (also in some other word pairs such as brass/brazen and staff/staves).

bath: short vowel in Middle English, lengthened during the Modern English period, in only some dialects

The vowel in “bath” was lengthened later on in some (but not all) dialects by a process that also lengthened a before the other voiceless fricatives /s/ and /f/ in certain contexts. But because the lengthening of a before voiceless fricatives happened later, it resulted in a different quality of the vowel. In southern British English, lengthened a in this context has the quality of a back vowel, [ɑː].

In some American English accents, "ath" words like "bath" instead show a lengthened or "tense" vowel with a front quality, which is realized phonetically in a variety of ways (e.g. [æə̯] or [eə̯]). But however it's pronounced, I have not heard of American English speakers merging the vowel in bath with the face vowel (which is [eɪ] or [e]).

A more detailed history

You only asked about the difference between the vowels, but here is an overview of the entire history of other differences between the words.

Here's a chart:

         PG       OE      Early ME    Later ME   Early ModE   SBE
 noun    *baþą    bæþ     [baθ]       [baθ]      [bæθ]        [bɑːθ] 

 verb    *baþōną  baþian  [baðə(n)]   [baːð(ə)]  [beɪð]       [beɪð]

Abbreviations: PG = Proto-Germanic, OE = Old English, ME = Middle English, ModE = Modern English, SBE = Southern British English

Between PG and OE, the sound changes of "Anglo-Frisian brightening" and "A-restoration" applied, creating the difference in Old English between æ in bæþ and a in baþian. Although marked in writing, the distinction between short æ and short a in Old English was barely contrastive and was lost in Middle English. (The Old English long vowels ǣ and ā, on the other hand, had a stronger contrast that did endure in later forms of the language.) The quoted Etymonline entry is wrong: i-mutation did not apply to either of these words. Even though baþian has an i, the i in the Class II weak verb suffix -ian did not cause i-mutation; this may be because it came from the Proto-Germanic suffix -ōną which had no *i. Fricative sounds like þ had "allophonic voicing" in Old English: at the end of a word, þ was pronounced [θ], while in the middle of a word between vowels, þ was pronounced [ð].

Between OE and Early Middle English, the vowel merger mentioned above turned the vowel in both words into short [a]. Vowel reduction caused the infinitive ending -ian to eventually become something like [ən]; word-final [n] could also be lost in this context, leaving only a schwa [ə]. Word-final schwa in Middle English was written with the letter "e", so Middle English forms like [baðə] (and others like it) are what's behind the "silent e" spelling pattern of "bathe". (I wrote a more detailed answer about "silent e" spellings here.)

During the Middle English period, final schwa sounds came to be lost, but not before causing a preceding short [a], [e] or [o] sound to lengthen to [aː], [ɛː] or [ɔː] respectively. (Lengthening of [i] and [u] happened only sometimes: the modern English "silent e" spelling patterns for the letters "i" and "u" have more complicated origins.) So by the Late Middle English period, bathe might be pronounced [baːð]. By this point, the distinction between [θ] and [ð] would be considered phonemic rather than allophonic as both sounds could occur in the same environment (at the end of a word). The loss of word-final schwa created a number of other pairs of words with alternations between voiced and voiceless word-final fricatives.

Between Middle English and Early Modern English, the Great Vowel Shift turned [aː] into [eɪ]. There were similarly large changes in the pronunciation of many other Middle English long vowel sounds. Middle English short [a] usually came to have a short front pronunciation [æ] in Modern English, but in some contexts it was backed and lengthened to [ɑː]. The history of that lengthening is really a separate question as it isn't relevant to why bath and bathe are pronounced differently.

| improve this answer | |
  • In some southern US accents, /æ/ can get somewhat close to [eɪ]. For example, according to Wikipedia, "ham" and "land" can have vowels somewhere between [eə] and [æjə]. Whether this is also true of "bath" I'm not sure. (Similarly, Wiktionary records a Southern pronunciation of "can't" as [kʰeɪnt].) To know for certain whether the OP was wrong about the American pronunciation of "bath", one would have to know how people speak in their part of the US. – rjpond Aug 21 at 17:34
  • 3
    In my experience living in the SE US, the /æ/ in "bath" can indeed fall "somewhere between [eə] and [æjə]." However, people with that accent still regard that as contrastive with [eɪ]. The pronunciation of "bathe" is pretty consistent across multiple US and UK accents, and I would be very surprised to hear an American say that they (or other Americans) pronounce "bath" with the same vowel sound as "bathe". – Mark Foskey Aug 21 at 19:48
  • 1
    The voicing of the verb's consonant goes hand in glove with this, as it does in other contrasting pairs where the noun in unvoiced and the verb voiced: breath/breathe, wreath/wreathe, sheath/sheathe, tooth/teethe, grief/grieve, belief/believe, house/house, serf/serve, safe/save, life/live, shelf/shelve, half/halve, calf/calve, wolf/wolve, cloth/clothe, delf/delve. It's why you get voiced versions in the plural nouns cloth/clothes, leaf/leaves, wife/wives, life/lives, knife/knives, elf/elves. Note also pairs gift/give, cleft/cleave, drift/drive, left/leave, heft/heave, bereft/bereave. – tchrist Aug 22 at 2:11
  • Much appreciated!!! – Melancholy Aug 22 at 10:21
  • @tchrist while the question was not about the consonant, I wouldn't mind seeing your comment in a full answer. – Mr Lister Aug 22 at 15:57

However it doesn't say anything about why "bath" has a long a vowel /bɑːθ/ and "bathe" has [...] /beɪð/.

In fact, it does:

"bathe (v.) Old English baþian "to wash, lave, place in a bath, take a bath" (transitive and intransitive), from root of bath (q.v.), with different vowel sound due to i-mutation.

i mutationenter image description here

| improve this answer | |
  • 2
    Etymonline is mistaken in saying this, though. Bath goes back to Old English bæð and bathe goes back to Old English baðian. While these old English words did happen to have slightly different vowel qualities, it's not because of i-mutation. It's because short a was "brightened" to æ in certain contexts in Old English. Old English short æ and short a barely contrasted and both merged in Middle English as short a. – herisson Aug 22 at 17:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.