Several symbols indicating secondary articulation have been dropped altogether, with the idea that such things should be indicated with diacritics: for is one.
They are to be distinguished from co-articulated consonants with secondary articulation, that is, a second articulation not of the same manner.
Labialization is the most widespread secondary articulation in the world's languages.
There are a number of secondary articulations.
The first three types of sounds above have a convex tongue shape, which gives them an additional secondary articulation of palatalization.
Russian has palatal secondary articulation of consonants, the so-called soft and hard sounds.
Terminology such as "palatal vowel" is found, but this is primary and not secondary articulation.
Northeast Caucasian phonology is also notable for its use of numerous secondary articulations as contrastive features.
However, there is a large number of common secondary articulations.
Usually, only one of these secondary articulations can co-occur with a given sound.