We all know that English has some odd sounds that few other languages possess. Among English’s inventory of strange consonants we find “th.”
Many people coming to English recently don’t realize that, although spelled exactly the same, there are, in fact, two ‘th” sounds – the voiceless “th” in words like three, things, theatre, breath, health, both; and the voiced “th” in words like though, then, this, breathe, soothe. Notice that in addition to the difference in “voicing” (whether or not the vocal cords are vibrating), the first one is much stronger than the second. But both are made by pressing the tongue against the back of the top teeth and forcing air through the narrow gap between, creating some friction and turbulence. Try it now: first the voiceless … and now the voiced … [repeat, please]
The sensation in your mouth will be similar to “f” and “v”; and “s” and “z” – sounds that are much more common among the world’s languages.
But which one should you use and when? Great question! And like so many questions about this odd language of mine, with its many irregularities and peculiarities, this one is hard to answer. For example, most English speakers pronounce “breath” with a voiceless “th,” but “breathe” with a voiced “th.” And the plural of “bath” (voiceless) is “baths” (voiced). And most dictionaries are no help, spelling both sounds as “th.”
A really good pronouncing dictionary, giving both British English and US English pronunciations in IPA (International Phonetic Alphabet) is Longman’s Pronunciation Dictionary, by J.C. Wells. See http://www.pearsonlongman.com/ae/dictionaries/LongPronDict.html. It’s always within easy reach of my desk, and in addition to providing the “standard” pronunciation (a very debatable term, of course) lists alternative pronunciations, even telling us what percentage of the population favors which pronunciation. Fans of English will love this book.
You many be confused about “th” when you listen to some English dialects. For example: someone with a strong London accent might pronounce “I thought I was through with those thirty-three thick and thorny thistles” using “f” and “d” sounds. (I’ll demonstrate.) Someone with a classic Brooklyn accent would use “t” and “d” sounds in their place. (I’ll demonstrate.) Much general American speech is also going in the same direction. “Th” is clearly on the endangered species list and may not survive this century.
But until then, here’s a fiendishly difficult little practice sentence to help anyone wishing to contribute to my “SAVE OUR ‘TH’” campaign: Mother’s fifth brother thought there was nothing soothing about three baths on Thursday.