I.Definition of phonetic features

When we describe segment in terms of places of articulation, manners of articulation, voicing, position of the tongue, height of the tongue, lip-rounding and tensity, we actually analyze speech sounds into their composing elements or phonetic features.

[g] possesses the features [+voiced] [+velar] [+stop]. There are other segments that possess one of the three features, but none that possessed all three. Those features are called phonetic features.

II. Natural classes

Classes of sounds that share a feature or features are called natural classes. The feature [+round] is shared by [uː], [u], [ɔː], [ɔ].

Features form a hierarchy. Some features specify a small class. E.g.

[+anterior] defines labiodentals, interdentals and alveolars, namely, [p], [b], [m], [f], [v], [θ], [ð], [t], [d], [l], [r], [n].

[+continuant] specifies all the fricatives, liquids and glides.

[+sibilant] (also called [+strident]) is a feature found in [s], [z], [ʃ], [ʒ] [tʃ],[ dʒ].

[+syllabic] is a feature that represents all the vowels and [m], [n], [l].

[+sonorant] is a major class feature. It is shared by all the vowels, nasals, liquids and glides.