/t/ and /d/ are probably among the most common phonemes in languages of the world, but their allophonic variants vary greatly from one language to another. In Japanese, /t/ and /d/ are usually either ‘lamino-dental’ (the tongue blade touching the upper teeth) or ‘lamino-alveolar’ (the tongue blade touching the alveolar ridge and the tongue tip resting on the lower teeth ridge). These two types of articulation are auditorily very similar to each other. English /t/ and /d/, on the other hand, are usually ‘apico-alveolar’, i.e., the tongue tip making contact with the alveolar ridge, whose auditory impression differs considerably from that of the Japanese /t/ and /d/. Alveolar consonants, or coronal articulations in general, are so tricky.
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