Vowel harmony
Compound words are considered separate words with respect to vowel harmony: vowels do not have to harmonize between members of the compound (thus forms like |"gün" "this|day" = "today" are permissible). Vowel harmony does not apply for loanwords, as in "otobüs" – from French "autobus". There are also a few native modern Turkish words that do not follow the rule (such as "anne" "mother" or "kardeş" "sibling" which used to obey vowel harmony in their older forms, "ana" and "karındaş", respectively). However, in such words, suffixes nevertheless harmonize with the final vowel; thus "annesi – "his/her mother", and "voleybolcu – "volleyball player".