Learn English – Why are “bath” and “bathe” pronounced differently

british-englishpronunciation

I'm specifically talking about British English. In British English, "bath" (noun) has a long vowel ([ɑː]) while the verb "bathe" has a diphthong ([eɪ]) 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" /beɪð/. 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.

Best Answer

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).

Examples:

  • 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:


+/f/ LAUGH, STAFF
+/ft/ RAFT, AFTER
+/mpl/ EXAMPLE, SAMPLE
+/nd/ COMMAND, DEMAND
+/ns/ ANSWER, FRANCE
+/n(t)ʃ/ BRANCH, RANCH
+/nt/ AUNT, ADVANTAGE
+/s/ GRASS, PASS
+/sk/ TASK, MASK
+/sp/ GRASP, CLASP
+/st/ FAST, NASTY
+/θ/ BATH, AFTERMATH

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.

Examples:

  • 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.

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