This question may or may not be specific to the General American accent.

In words such as thin, thick, and throw, the initial /θ/ doesn't sound the same as the /θ/ in words such as math and wrath. I understand that phonemically they are both (voiceless) dental fricatives, but the initial ⟨th⟩ sounds like a plosive or aspirated dental fricative or stop. What is phonetic realization of initial ⟨th⟩ in the English language?

2 Answers 2


You are comparing consonants at the beginning of a syllable with consonants at the end. Consonants at the beginning are fortis, while those at the end are lenis. This is a very general difference in English and in some other languages. Saussure called syllable onset, fortis, consonants explosive, and he called syllable offset, lenis consonants, implosive (in Course in General Linguistics).

Fortis consonants use more muscular effort, and consequently for the dental fricatives, the tongue is pressed more forcefully against the upper teeth. This makes the obstruction to the stream of air through the mouth smaller and makes it last longer. More air pressure will build up in the mouth, behind the obstruction, and when the consonant is released, there will be a larger explosion of air than for the corresponding lenis consonant in the offset of a syllable.

Lenis consonsonants are more subject to lenitive changes, such as assimilation, than fortis consonants. In English "tenth", the final "th" can assimilate to the preceding (nasal) stop to become a dental stop.

  • In English "tenth", the final "th" can assimilate to the preceding (nasal) stop to become a dental stop. In what dialect(s) does this happen? I don't think I've ever heard tenth pronounced with a final stop (except in Irish English where th is generally pronounced [t̪]).
    – TKR
    Oct 17, 2015 at 23:40
  • @TKR, It happens in my speech. I haven't done a survey.
    – Greg Lee
    Oct 18, 2015 at 0:39

In my first teaching gig, I was explaining the use of θ to represent the fricative in "thin", and a student later asked me about the "th" in "thin"... which she pronounced as a dental stop, so [t̪ʰin] "thin" vs [tʰɪn] "tin". She was from urban New Jersey. If you have a recording, it should be easy to determine exactly what the difference is (if any), but I would go with a dental / alveolar stop distinction as a first guess.

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