Pronunciation of English ⟨th⟩

In English, the digraph 〈th〉 represents in most cases one of two different phonemes: the voiced dental fricative /ð/ (as in this) and the voiceless dental fricative /θ/ (thing). More rarely, it can stand for /t/ (Thailand) or the consonant cluster /th/ (lighthouse).

Phonetic realisation

General description

In standard English, both in Britain and America, the phonetic realisation of the dental fricative phonemes shows less variation than for many other English consonants. Both are pronounced either interdentally, with the blade of the tongue resting against the lower part of the back of the upper teeth and the tip protruding slightly (though less prominently than for the corresponding sound in Spanish) or alternatively with the tip of the tongue against the back of the upper teeth. The interdental position might also be described as "apico" or "lamino-dental". These two positions may be free variants, but for some speakers they are complementary allophones, the position behind the teeth being used when the dental fricative stands in proximity to an alveolar fricative, as in clothes (/ðz/) or myths (/θs/). Lip configuration may vary depending on phonetic context. The vocal folds are abducted. The velopharyngeal port is closed. Air forced between tongue surface and cutting edge of the upper teeth (interdental) or inside surface of the teeth (dental) creates audible frictional turbulence.

The difference between gooses and geese is normally described as a MONKEY contrast, as this is the aspect native speakers are most aware of. However the two phonemes are also distinguished by other phonetic markers. There is a difference of energy (see: Fortis and lenis), the fortis /θ/ being pronounced with more muscular tension than the lenis /ð/. Also, /θ/ is more strongly aspirated than /ð/, as can be demonstrated by holding a hand a few centimeters in front of the mouth and noticing the differing force of the puff of air created by the articulatory process.

As with many English consonants, a process of assimilation can result in the substitution of other speech sounds in certain phonetic environments. Most surprising to native speakers, who do this subconsciously, is the use of [n] and [l] as realisations of /ð/ in the following phrases:^[1]

join the army: /ˈdʒɔɪn ði ˈɑmi/ → [ˈdʒɔɪn ni ˈɑmi]

fail the test: /feɪl ðə ˈtɛst/ → [feɪl lə ˈtɛst]

/θ/ and /ð/ can also be lost through elision. In rapid speech, sixths may be pronounced like six. Them may be contracted to 'em, and in this case the contraction is often indicated in writing. (In fact, 'em is originally a separate word, a remnant of Old English hem, but as the apostrophe shows, it is conceived in modern English as a contraction.^[2])

Realisation in non-standard Englishes

In some areas such as London, many people realize the phonemes /θ/ and /ð/ as [f] and [v] respectively (th-fronting). Although stigmatized as typical of a Cockney accent, this pronunciation is fairly widespread, and in at least one case has been transferred into standard English as a neologism: a bovver boy is a thug, a "boy" who likes "bother" (fights).

Many speakers of Hiberno-English use a voiceless dental plosive /t̪, d̪/ (still usually distinct from alveolar /t, d/) instead of, or in free variation with, the fricatives /θ, ð/ (th-stopping). In African American Vernacular English, /ð/ is often pronounced [d], especially in unstressed words (for example the, them, with).

Acquisition problems

Children generally learn the less marked phonemes of their native language before the more marked ones. In the case of English-speaking children, /θ/ and /ð/ are often among the last phonemes to be learned, frequently not being mastered before the age of five. Prior to this age, many children substitute the sounds [f] and [v] respectively. For small children, fought and thought are therefore homophones. As British and American children begin school at five, this means that many are learning to read and write before they have sorted out these sounds, and the infantile pronunciation is frequently reflected in their spelling errors: ve fing for the thing.

Children with a lisp, however, have trouble distinguishing /θ/ and /ð/ from /s/ and /z/ respectively, using a single [s̪] or [z̪] pronunciation for both, and may never master the correct sounds without speech therapy. This is by far the most common speech impediment in English.

Foreign learners may have parallel problems. In English popular culture the substitution of /z/ for /ð/ is a common way of parodying a French accent, but in fact learners from very many cultural backgrounds have difficulties with English dental fricatives, usually caused by interference with either sibilants or stops. Words with a dental fricative adjacent to an alveolar sibilant, such as clothes, truths, fifths, sixths, anesthetic, etc., are commonly very difficult for foreign learners to pronounce.

A famous advert for Berlitz language school plays on the difficulties Germans may have with dental fricatives: see Ze German Coastguard.

Phonology and distribution

In modern English, /θ/ and /ð/ bear a phonemic relationship to each other, as is demonstrated by the presence of a small number of minimal pairs: thigh:thy, ether:either, loath:loathe. They are distinguished from the neighbouring labeo-dental fricatives, sibilants and alveolar stops by such minimal pairs as thought:fought/sought/taught and then:Venn/Zen/den.

The vast majority of words in English with 〈th〉 have /θ/, and almost all newly created words do. However, the constant recurrence of the function words, particularly the, means that /ð/ is nevertheless more frequent in actual use.

The distribution pattern may be summed up in the following rule of thumb which is valid in most cases: in initial position we use /θ/ except in function words; in medial position we use /ð/ except for foreign loan words; and in final position we use /θ/ except in verbs. A more detailed explanation follows.

Initial position

Almost all words beginning with a dental fricative have /θ/.
A small number of common function words (the Middle English anomalies mentioned below) begin with /ð/. The words in this group are:

5 demonstratives: the, this, that, these, those
2 personal pronouns each with four forms: thou, thee, thy, thine; they, them, their, theirs
7 adverbs and conjunctions: there, then, than, thus, though, thence, thither (though some speakers pronounce thence and thither with initial /θ/)
Various compound adverbs based on the above words: therefore, thereupon, thereby, thereafter, thenceforth, etc.

But note also the few words with initial 〈th〉 for /t/ (e.g. Thomas): see below.

Medial position

Most native words with medial 〈th〉 have /ð/.

Between vowels: heathen, fathom; and the frequent combination -ther-: bother, brother, dither, either, father, Heather, lather, mother, other, rather, slither, southern, together, weather, whether, wither, smithereens; Caruthers, Gaithersburg, Netherlands, Witherspoon, and similar compound names where the first component ends in '-ther' or '-thers'. But Rutherford has either /ð/ or /θ/.
Preceded by /r/: Worthington, farthing, farther, further, northern.
Followed by /r/: brethren.

A few native words have medial /θ/:

The adjective suffix -y normally leaves terminal /θ/ unchanged: earthy, healthy, pithy, stealthy, wealthy; but worthy and swarthy have /ð/.
Compound words in which the first element ends or the second element begins with 〈th〉 frequently have /θ/, as these elements would in isolation: bathroom, Southampton; anything, everything, nothing, something.
The only other native word with medial /θ/ would seem to be brothel.

Most loan words with medial 〈th〉 have /θ/.

From Greek: Agatha, anthem, atheist, Athens, athlete, cathedral, Catherine, Cathy, enthusiasm, ether, ethics, ethnic, lethal, lithium, mathematics, method, methyl, mythical, panther, pathetic, sympathy
From Latin: author, authority (though in Latin these had /t/; see below). Also names borrowed from or via Latin: Bertha, Gothic, Hathaway, Jonathan, Othello, Parthian
From Celtic languages: Arthur (Welsh has /θ/ medially: /ærθɨr/); Abernathy, Abernethy
From German: Luther, as an anglicized spelling-pronunciation (see below).

Loanwords with medial /ð/:

Greek words with the combination -thm-: algorithm, logarithm, rhythm. Also asthma, though here the 〈th〉 is nowadays usually silent.

Note also the few words with medial 〈th〉 for /t/ or /th/ (e.g. lighthouse): see below.

Final position

Nouns and adjectives

Nouns and adjectives ending in a dental fricative usually have /θ/: bath, breath, cloth, froth, loath, sheath, sooth, tooth/teeth, wreath.
Exceptions are usually marked in the spelling with 〈-the〉: tithe, lathe, lithe with /ð/.
blythe, booth, scythe, smooth have either /ð/ or /θ/.

Verbs

Verbs ending in a dental fricative usually have have /ð/, and are frequently spelled 〈-the〉: bathe, breathe, clothe, loathe, scathe, scythe, seethe, sheathe, soothe, teethe, tithe, wreathe, writhe. Spelled without 〈e〉: mouth (verb) nevertheless has /ð/.
froth has either /θ/ or /ð/ as a verb, but /θ/ only as a noun.
The verb endings -s, -ing, -ed do not change the pronunciation of a 〈th〉 in the final position in the stem: bathe has /ð/, therefore so do bathed, bathing, bathes; frothing with either /θ/ or /ð/. Likewise clothing used as a noun, scathing as an adjective etc.

Others

with has either /θ/ or /ð/ (see below), as do its compounds: within, without, outwith, withdraw, withhold, withstand, wherewithal, etc.

Plurals

Plural 〈s〉 after 〈th〉 may be realised as either /ðz/ or /θs/:

Some plural nouns ending in 'ths', with a preceding vowel, have /ðz/, although the singulars always have /θ/; however a variant in /θs/ will be found for many of these: baths, booths, oaths, paths, sheaths, truths, wreaths, youths exist in both varieties; clothes always has /ðz/.
Others have only /θs/: azimuths, breaths, cloths, deaths, faiths, Goths, growths, mammoths, moths, mouths, myths, smiths, sloths, zeniths, etc. This includes all words in 'th' preceded by a consonant (earths, hearths, lengths, months, widths, etc.) and all numeric words, whether preceded by vowel or consonant (fourths, fifths, sixths, sevenths, eighths /eɪtθs/, twelfths, fifteenths, twentieths, hundredths /hʌndrədθs/, thousandths).

Grammatical alternation

In pairs of related words, an alternation between /θ/ and /ð/ is possible, which may be thought of as a kind of consonant mutation. Typically [θ] appears in the singular of a noun, [ð] in the plural and in the related verb: cloth /θ/, clothes /ð/, to clothe /ð/. This is directly comparable to the /s/-/z/ or /f/-/v/ alternation in house, houses or wolf, wolves. It goes back to the allophonic variation in Old English (see below), where it was possible for 〈þ〉 to be in final position and thus voiceless in the basic form of a word, but in medial position and voiced in a related form. The loss of inflections then brought the voiced medial consonant to the end of the word. Often a remnant of the old inflection can be seen in the spelling in the form of a silent 〈e〉, which may be thought of synchronically as a marker of the voicing.

Regional differences in distribution

The above discussion follows Daniel Jones' English Pronouncing Dictionary, the authority on standard British English, and Webster's New World College Dictionary, an authority on American English. Usage appears much the same between the two. Regional variation within standard English includes the following:

The final consonant in with is pronounced /θ/ (its original pronunciation) in northern Britain, but /ð/ in the south, though some speakers of Southern British English use /θ/ before a voiceless consonant and /ð/ before a voiced one. A 1993 postal poll of American English speakers showed that 84% use /θ/, while 16% have /ð/ (Shitara 1993). (The variant with /ð/ is presumably a sandhi development.)
In Scottish English, /θ/ is found in many words which have /ð/ further south. The phenomenon of nouns terminating in /θ/ taking plurals in /ðz/ does not occur in the north. Thus the following have /θs/: baths, mouths (noun), truths. Scottish English does have the termination /ðz/ in verb forms, however, such as bathes, mouths (verb), loathes, and also in the noun clothes, which is a special case, as it has to be clearly distinguished from cloths. Scottish English also has /θ/ in with, booth, thence etc., and the Scottish pronunciation of thither, almost uniquely, has both /θ/ and /ð/ in the same word. Where there is an American-British difference, the North of Britain generally agrees with America on this phoneme pair.

History of the English phonemes

Germanic origins

Proto-Indo-European (PIE) had no dental fricatives, but these evolved in the earliest stages of the Germanic languages. In Proto-Germanic, /ð/ and /θ/ were separate phonemes, usually represented in Germanic studies by the symbols *đ and *þ.

*đ (/ð/) was derived by Grimm's law from PIE *dʰ or by Verner's law (i.e. when immediately following an unstressed syllable) from PIE *t.
*þ (/θ/) was derived by Grimm's law from from PIE *t.

In West Germanic, the Proto-Germanic *đ shifted further to *d, leaving only one dental fricative phoneme. However, a new [ð] appeared as an allophone of /θ/ in medial positions by assimmilation of the voicing of the surrounding vowels. [θ] remained in initial and presumably in final positions (though this is uncertain as later terminal devoicing would in any case have eliminated the evidence of final [ð]). This West Germanic phoneme, complete with its distribution of allophones, survived into Old English. In German and Dutch, it shifted to a /d/, the allophonic distinction simply being lost. In German, West Germanic *d shifted to /t/ in what may be thought of as a chain shift, but in Dutch, *þ, *đ and *d merged into a single /d/.

The whole complex of Germanic dentals, and the place of the frictatives within it, can be summed up in this table:

PIE	Proto-Germanic	West Germanic	Old English	German	Dutch	Notes
*t	*þ	*[þ]	[θ]	/d/	/d/	Original *t in initial position, or in final position after a stressed vowel
	*þ	*[đ]	[ð]	/d/		Original *t in medial position after a stressed vowel
	*đ	*d	/d/	/t/		Original *t after an unstressed vowel
*dʰ	*đ	*d	/d/	/t/		Original *dʰ in all positions
*d	*t	*t	/t/	/s/ or /ts/	/t/	Original *d in all positions

For more on these phonemes from a comparative perspective, see Grammatischer Wechsel. For the developments in German and Dutch see High German consonant shift.

Old English

Thus English inherited a phoneme /θ/ in positions where other West Germanic languages have /d/ and most other Indo-European languages have /t/: English thou, German du, Latin tu.

In Old English, the phoneme /θ/, like all fricative phonemes in the language, had two allophones, one voiced and one voiceless, which were distributed regularly according to phonetic environment.

[ð] (like [v] and [z]) was used between two voiced sounds (either vowels or voiced consonants).
[θ] (like [f] and [s]) was spoken in initial and final position, and also medially if adjacent to another unvoiced consonant.

Although Old English had two graphemes to represent these sounds,〈þ〉(thorn) and 〈ð〉 (eth), it used them interchangeably, unlike Old Icelandic, which used 〈þ〉 for /θ/ and 〈ð〉 for /ð/.

Development up to Modern English

The most important development on the way to modern English was the investing of the existing distinction between [ð] and [θ] with phonemic value. This has been called the then-thyn split. Minimal pairs, and hence the phonological independence of the two phones, developed as a result of three main processes.

In early Middle English times, a group of very common function words beginning with /θ/ (the, they, there, etc.) came to be pronounced with /ð/ instead of /θ/. Possibly this was a sandhi development; as these words are frequently found in unstressed positions they can sometimes appear to run on from the preceding word, which may have resulted in the dental fricative being treated as though it were word-internal.

English has borrowed many words from Greek. Where the original Greek had the letter 〈θ〉 (theta), English retained the Late Greek pronunciation /θ/, regardless of phonetic environment. In a few words of Indian origin, such as thug, 〈th〉 represents Sanskrit थ (/tʰ/) or ठ (/tTemplate:Latinx/), usually pronounced /θ/ (but occasionally /t/) in English.

English has lost its original verb inflections. When the stem of a verb ends with a dental fricative, this was usually followed by a vowel in Old English, and was therefore voiced. It is still voiced in modern English, even though the verb inflection has disappeared leaving the /ð/ at the end of the word. Examples are to bathe, to mouth, to breathe.

Other changes which affected these phonemes included a shift /d/ → /ð/ when followed by unstressed suffix -er. Thus Old English fæder became modern English father; likewise mother, gather, hither, together, weather. In a reverse process, Old English burthen and murther become burden and murder.

Dialectally, the alternation between /d/ and /ð/ sometimes extends to other words, as bladder, ladder, solder with /ð/. On the other hand some dialects retain original d, and extend it to other words, as brother, further, rather. The Welsh name Llewelyn appears in older English texts as Thlewelyn (Rolls of parliament (Rotuli parliamentorum) I. 463/1, King Edward I or II), and Fluellen (Shakespeare, Henry V). Th also occurs dialectally for wh, as in thirl, thortleberry, thorl, for whirl, whortleberry, whorl. Conversely, Scots has whaing, whang, white, whittle, for thwaing, thwang, thwite, thwittle.

The old verb inflection -eth (Old English -eþ) was replaced by -s (he singeth → he sings), not a sound shift but a new completely inflection, the origin of which is still being debated.

History of the digraph

〈th〉 for /θ/ and /ð/

Though English speakers take it for granted, the digraph 〈th〉 is in fact not an obvious combination for a dental fricative. The origins of this have to do with developments in Greek.

Proto-Indo-European had an aspirated /dʰ/ which came into Greek as /tʰ/, spelled with the letter theta. In the Greek of Homer and Plato this was still pronounced /tʰ/, and therefore when Greek words were borrowed into Latin theta was transcribed with 〈th〉. Since /tʰ/ sounds like /t/ with a following puff of air, 〈th〉 was the logical spelling in the Latin alphabet.

By the time of New Testament Greek (koiné), however, the aspirated stop had shifted to a fricative: /tʰ/→/θ/. Thus theta came to have the sound which it still has in Modern Greek, and which it represents in the IPA. From a Latin perspective, the established digraph 〈th〉 now represented the voiceless fricative /θ/, and was used thus for English by French-speaking scribes after the Norman Conquest, since they were unfamiliar with the Germanic graphemes ð (eth) and þ (thorn). Likewise, the spelling 〈th〉 was used for /θ/ in Old High German prior to the completion of the High German consonant shift, again by analogy with the way Latin represented the Greek sound.

The history of the digraphs 〈ph〉 for /f/ and 〈ch〉 for Scots or German /x/ is parallel.

〈th〉 for /t/

Since neither /tʰ/ nor /θ/ was a native sound in Latin, the tendency must have emerged early, and at the latest by medieval Latin, to substitute /t/. Thus in many modern languages, including French and German, the 〈th〉 digraph is used in Greek loan-words to represent an original /θ/, but is now pronounced /t/: examples are French théâtre, German Theater. In some cases, this etymological 〈th〉, which has no remaining significance for pronunciation, has been transferred to words in which there is no etymological justification for it. For example German Tal ('valley', cognate with English dale) appears in many place-names with an archaic spelling Thal (see Neanderthal). The names Gunther and Beethoven are other examples. The German spelling reform of 1901 largely reversed these, but they remain in some proper nouns.

Examples of this are also to be found in English, perhaps influenced immediately by French. In some Middle English manuscripts, 〈th〉 appears for 〈t〉 or 〈d〉: tho 'to' or 'do', thyll till, whythe white, thede deed. In Modern English we see it in Esther, Thomas, Thames, thyme, and the old spelling of Satan as Sathan. In a small number of cases, this spelling later influenced the pronunciation: amaranth, amianthus and author have spelling-pronunciations with /θ/, and some English speakers use /θ/ in Neanderthal.

〈th〉 for /th/

A few English compound words, such as lightheaded or hothouse, have the letter combination 〈th〉 split between the parts, though this is not a digraph. Here, the 〈t〉 and 〈h〉 are pronounced separately (light-headed) as a cluster of two consonants. Other examples are anthill, outhouse, lighthouse, pothead, Chatham, Wytham, Yetholm; also in words formed with the suffix -hood: knighthood, and the similarly formed Dutch loanword apartheid.

Notes

^ examples from Collins and Mees p. 103
^ Online Etymology Dictionary. 'em. Retrieved on 18 September 2006.

References

Beverly Collins and Inger M. Mees (2003), Practical Phonetics and Phonology, Routledge, ISBN 0-415-26133-3.
Shitara, Yuko (1993). "A survey of American pronunciation preferences." Speech Hearing and Language 7: 201–32.