PLACES OF ARTICULATION
The active articulator usually moves in order to make the constriction. The passive articulator usually just sits there and gets approached. A sound's place of articulation is usually named by using the Latin adjective for the active articulator (ending with an "o") followed by the Latin adjective for the passive articulator. For example, a sound where the tongue tip (the "apex") approaches or touches the upper teeth is called an "apico-dental". Most of the common combinations of active and passive articulator have abbreviated names (usually leaving out the active half). These are the abbreviated names for the places of articulation used in English: Bilabial
The articulators are the two lips. (We could say that the lower lip is the active articulator and the upper lip the passive articulator, though the upper lip usually moves too, at least a little.) English bilabial sounds include [p], [b], and [m]. [pic] Labio-dental
The lower lip is the active articulator and the upper teeth are the passive articulator. English labio-dental sounds include [f] and [v]. [pic] Dental
Dental sounds involve the upper teeth as the passive articulator. The active articulator may be either the tongue tip or (usually) the tongue blade. Dentals are the initial sounds of words ‘thin’ and ‘that’.[pic] Alveolar
Alveolar sounds involve the alveolar ridge as the passive articulator. The active articulator may be either the tongue blade or (usually) the tongue tip. English alveolar sounds include [t], [d], [n], [s], [z], [l]. [pic] Post alveolar
Post alveolar sounds involve the area just behind the alveolar ridge as the passive articulator. The active articulator may be either the tongue tip or (usually) the tongue blade. English postalveolars include [[pic]r ]. [pic] Linguists have traditionally used very inconsistent terminology in referring to the post alveolar POA. Some of the terms you may encounter for it include: palato-alveolar, alveo-palatal,...