Consonant gemination or length is contrastive. Consonant length (gemination) is also phonemic. The symbol ( ') indicates gemination or consonant doubling. While Japanese features consonant gemination, there are some limitations in what can be geminated. The second is predictive gemination of initial consonants on morpheme boundaries. It also makes use of the gemination of stops, fricatives and sonorants. Before other stops and fricatives, it assimilates, creating an effect of gemination. A few cases of gemination do not correspond to double consonant letters in the orthography. It denotes the gemination of the initial consonant of the kana that follows it. Vowel gemination can also sometimes illustrate semantic change. There is some dispute about how gemination fits with Japanese phonotactics. All of these languages do have the "northwest" characteristics of lenition and loss of gemination. "Swebban" "to put to sleep" is a class-one verb exhibiting gemination and an epenthetic vowel. However, phonetic gemination does occur marginally. These fortis and lenis stops may have been distinguished by either voicing or gemination.