Later commentaries additionally suggested that the true pronunciation of this name is composed entirely of vowels, such as the Greek Ιαουε. However, this is put into question by the fact that vowels were only distinguished in the time-period by their very absence due to the lack of explicit vowels in the Hebrew script. The resulting substitute made from semivowels and glottals, known as the tetragrammaton, is not ordinarily permitted to be pronounced aloud, even in prayer. The prohibition on misuse (not use) of this name is the primary subject of the command not to take the name of the Lord in vain.