This Since the only case where the central versus

This parameter is rather a minor one, since it
distinguishes only one phoneme of English from all others. For almost all
English consonants, the airflow through the oral cavity is central. Recall that
fricatives, like s or f , are produced with close approximation of the
active and passive articulators; however, if you produce any fricative, you
will feel that your articulators are actually pushed together quite tightly at
the sides of the oral cavity, with the actual close approximation, and hence
the narrow gap for airflow, left in the middle. The same is true for all the
approximants except one: if you produce rip and lip, and focus on
the initial consonants, you will notice that while the outgoing air for /r/, as
usual, moves along the centre of the mouth, for /l/ it moves down the sides. If
you find this difficult to feel, try making the related voiceless fricative
sound found in Welsh names spelled with , like Llewellyn;
because this is a fricative and involves close approximation of the
articulators, the airflow is easier to observe. Alternatively, try making an l
ingressively, pulling the air into your mouth instead of breathing it out, and
feel the cold air moving inwards along the sides of your tongue. In English,
both the clear and the dark allophones of /l/, and only these, have lateral
airflow, and are known as lateral approximants. Since the only case where the
central versus lateral difference is distinctive in English involves /r/ and
/l/, these should consistently be described as central and lateral
respectively. Although in a particularly thorough description, all other sounds
(except nasals, which have no oral airflow at all) should be explicitly stated
to be central, this definition will generally be understood rather than stated
below, since the other English sounds do not contrast with lateral sounds of
the same place and manner of articulation, meaning that confusion is highly
unlikely.