The vowel accompanying each of these letters may differ from those listed above, depending on the first letter or vowel following it. The rules governing these changes are hardly observed in colloquial speech as most speakers tend to employ the regular form. However, they may be heard in more formal circumstances. For example, if a preposition is put before a word that begins with a moving Shva, then the preposition takes the vowel (and the initial consonant may be weakened): colloquial "be-kfar" (= "in a village") corresponds to the more formal "bi-khfar".