2 adjectives to describe semivowels

OF THE LETTER M. The consonant M is a semivowel and a liquid, capable of an audible, humming sound through the nose, when the mouth is closed.

I have shown also, that the sounds of all the other vowels, and of the consonant semivowels, may be prolonged to what degree we please; but at the same time it is to be observed, that all these may also be reduced to a short quantity, and are capable of being uttered in as short a space of time as those which are naturally short.

2 adjectives to describe  semivowels