T and th is a confusing pair when it comes to pronouncing consonants in Vietnamese. Although Vietnamese and English use the same alphabet, the letters t and th are pronounced differently in each language.
/t/: "T" is articulated with the tip of the tongue touching the upper teeth or gum ridge, closer to a dental position. It's like the unaspirated (very little puff of air) /t/ in the consonant cluster "st" in the words: "stop", "start", etc., not the /t/ at the start of a stressed syllable in the words: "top", "table".
/th/: "Th" is an aspirated dental/alveolar stop — similar in airflow to English "t" (with a puff of air), but with a tongue position closer to Vietnamese "t". Hold the air briefly in the mouth, keeping the tongue pressed against the teeth. Release the tongue and let out a strong puff of air as the sound is produced. It's much like the English "t", not the fricatives "th" in "think" /θ/ or "this" /ð/.
Now let's practice distinguishing t and th in Vietnamese with this worksheet.
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