Geminate consonants are phonemically contrastive in Biblical Hebrew. Nobiin is a tonal language with contrastive vowel and consonant length. Vowel length is phonologically contrastive and so is phonemic. Dinka has a rich vowel system, with thirteen phonemically contrastive short vowels. Word stress is not phonemically contrastive in Standard Arabic. Kolyma Yukaghir demonstrates contrastive vowel length. A number of languages use breathy voicing in a phonologically contrastive way. Phonemes that are contrastive in certain environments may not be contrastive in all environments. The contrastive mechanism is the vowel phonation. The labiodental fricative is only contrastive in loanwords. Marquesan distinguishes between two contrastive types of possession. Premodifying adjectives in hyperbaton often have focus or contrastive emphasis. All consonants also come in short and long forms, which are contrastive. It is now widely held that Old Chinese did not have phonemically contrastive tone. When there is no contrastive vowel sequence in the language, the diacritic may be omitted.