How to make this sound:

The two 'th' sounds:  just like [] and [], [] and [], etc., there is an unvoiced version [] and a voiced version [].  In the video texts, I refer to the unvoiced sound as 'th' and the voiced as 'dth'.  But it's better to watch the video than to read the text!

Video Text:

Th and dth are paired together because they take the same mouth position.  Th is unvoiced, you make the sound with just air, and dth voiced, you use the vocal cords to produce the sound.  The mouth position.  As you can see, the mouth comes through the teeth, but it is only the tip of the tongue.  Sometimes when people are learning, they use too much of their tongue, dth.  That will make it very difficult to speak.  Also, a common mistake is to not put the tongue through the teeth at all, and make a dd sound.  Dd.  That is also not correct.  Make sure just the tip of the tongue comes through your teeth:  th.  Sample word pairs: because I think it is especially helpful for these sounds, I'm going to go through them once slow and once normal.  {All pairs are in the order unvoiced, voiced} Thin, this ... theif, these ... birthday, worthy ... thin, this ... theif, these ... birthday, worthy.

International Phonetic Alphabet symbols: [] (as in thin), [] (as in this)

See Wikipedia's pages on these voiced and unvoiced sounds for technical descriptions and their occurrences in other langages.