What is the difference between double, secondary and primary articulation?

Question

I'm studying the secondary and double articulation, but got confused. Is double and primary articulation the same thing or what is the difference?

Answer 1

Secondary articulation refers to a "lesser" constriction, compared to the constriction of primary place of articulation. So in [tʷ, sʷ], the primary place of articulation is alveolar, and there is a secondary (vocalic-ish) labial articulation. Typically, secondary articulations are glide-like. "Double articulation" refers to segments which have two places of constriction which as "equal" in terms of constriction, for example [kp]. The phonological analysis of double articulations is controversial (the majority of evidence indicates that one of the places is indeed primary, but languages can differ in their analysis so that [kp] may behave like a "very labialized velar", or a "very velarized labial". Also note that these terms are quite variable in their use, so that [kʷ] may be called a "double articulation".