There are different ways to write with tengwar, which are called "modes". Between these modes there are differences, sometimes only a few and sometimes many differences. In different modes, the tengwar sometimes mean different sounds. In some modes the tengwar are used for vowels and consonants; and in other modes the tengwar are only used for the consonants, and the vowels are marked by signs above or below the tengwa, as in abugida writing. These vowel signs are called tehtar ("signs"; singular: "tehta", "sign").