This is a tricky pair of sounds because although they are always spelled the same way, “T.H.”, they can be pronounced as either voiced: “TH” or unvoiced. As ever, if you are confused, the dictionary will always help you. Phonetically, the voiced “TH”, as in This, symbol is a sort of “o” with a little “x” on top and the unvoiced “TH”, as in Thing, symbol is a zero with a horizontal line through the middle.
Where this sound can go wrong is when the unvoiced “TH” wrongly becomes a “FFF” sound so that “thing” is mispronounced as “fing”.
Also, the voiced “TH” can wrongly become a “V” so “this and that” become “vis and vat”. Watch out for these common mistakes!
Let’s practice the unvoiced “TH” sound with all the vowels.