Co-articulated consonants or complex consonants are consonants produced with two simultaneous places of articulation. They may be divided into two classes: doubly articulated consonants with two primary places of articulation of the same manner (both stop, or both nasal, etc.), and consonants with secondary articulation, that is, a second articulation not of the same manner.^[1]: 328

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An example of a doubly articulated consonant is the voiceless labial-velar stop [k͡p], which is pronounced simultaneously at the velum (a [k]) and at the lips (a [p]).

In practically all languages of the world that have doubly articulated consonants, these are either clicks or labial-velars.

An example of a consonant with secondary articulation is the voiceless labialized velar stop [kʷ] has only a single stop articulation, velar [k], with a simultaneous approximant-like rounding of the lips.

There is a large number of common secondary articulations. The most frequently encountered are labialization (such as [kʷ]), palatalization (such as the Russian "soft" consonants like [pʲ]), velarization (such as the English "dark" el [lˠ]), and pharyngealization (such as the Arabic emphatic consonants like [tˤ]).

As might be expected from the approximant-like nature of secondary articulation, it is not always easy to tell whether a co-articulated approximant consonant such as /w/ is doubly or secondarily articulated. In some English dialects^[which?], for example, /w/ is a labialized velar that could be transcribed as [ɰʷ].

The glottis controls phonation, and works simultaneously with many consonants. It is not normally considered an articulator, and an ejective such as [kʼ], with simultaneous closure of the velum and glottis, is not normally considered to be a co-articulated consonant.

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