"Degree of stricture" means how narrow the gap is between the active articulator and the passive articulator at the narrowest point in the vocal tract. We shall distinguish three degrees of constriction: i) complete closure, ii) close approximation, iii) open approximation. "Complete closure" is self-explanatory. "Close approximation" means "so close together that it causes audible friction". "Open approximation" means that the oral tract is somewhat more open than in "close approximation", so that there is no friction. Consequently, the three degrees of stricture are associated with different kinds of consonants and vowels:
2. Close approximation - fricatives;
3. Open approximation - approximants (liquids and semivowels) and vowels.
Of these, English provides examples of stops [p], [b], [t], [d], [k] and [ɡ]; nasals [m], [ɱ], [n] and [ŋ]; fricatives [f], [v], [θ], [ð], [s], [z], [ʃ], [ʒ] and [h]; and approximants [ɹ], [l], [j] and [w].
Apart from uvular and pharyngeal consonants, the remaining IPA stops and fricatives are made at the same set of places of articulation and with the same range of degrees of stricture as in English, but in different combinations.
Practise: