These characters are compiled into two syllabaries&colon; hiragana and katakana. The Japanese kana syllabaries indicate voiced consonants with marks known as dakuten. In the alphabets and syllabaries, individual written characters represent sounds only, rather than entire concepts. Irregularities within this awkward system led Japanese scribes to develop phonetically regular syllabaries. In 1877, Julius Oppert introduced "digraphique" to describe languages written in cuneiform syllabaries. Nearly all other scripts invented by illiterates are syllabaries like Cherokee. However, unlike true syllabaries, there is not an independent glyph for each syllable. The concept can also be applied to nonalphabetic writing systems like syllabaries. However, syllabaries with much larger inventories do exist. Syllabaries, such as Japanese katakana, are also handled this way (Wabun code). Based on the differing sources spanning centuries, the documented syllabaries also differed in form. Syllabaries are best suited to languages with relatively simple syllable structure, such as Japanese. Syllabaries are best suited to languages with a relatively simple syllable structure, such as Japanese.