Accent improvement focuses on teaching students how to pronounce difficult sounds such as , , , , and ; intonation, stress, and rhythm. Spanish and Portuguese speakers might add an before the vowel , as in "his" for "is". Therefore, vowel sounds are also covered in accent reduction training. Practicing of the vowel most commonly spelled "i" is done by reciting a few of the following differences: his versus is, hit versus it, hill versus ill. By not letting the back of their tongue touch the palate, native speakers of Asian languages (Chinese, etc.) can avoid adding a before the for example in speaking "yin" instead of "in".