In
phonetics, a sonorant is a
sound that can be made
continuously without
friction. All
vowels are sonorants, and so are some
consonants that block the mouth but allow the
air stream to escape unimpeded.
Nasal consonants block the mouth at some point (m is closed at the lips, n by the tongue against the teeth or the alveolar ridge behind the teeth); but the velum or soft palate is lowered allowing the air to escape through the nose.
Lateral consonants (sounds like l) block the mouth at one side only, but the passage is clear on the other.
The opposite of a sonorant is an obstruent.
Sometimes the word is restricted to only sonorant consonants.