43. Vowels are divided according to the position of the tongue. Latin
#i# and #e# are called _front vowels_, because the front part of the
tongue is elevated. This elevation is greater for #i# than for #e#.
Latin #o# and #u# are called _back vowels_, because they require an
elevation of the rear part of the tongue. This elevation is greater for
#u# than for #o#. Latin #a# holds an intermediate position, no part of
the tongue being raised, while the front part is depressed.
44. In the formation of #i# and #e#, the tongue approaches the hard
palate; hence these two vowels are also called _palatal vowels_.
Similarly, #o# and #u# are called _velar_ or _guttural vowels_, because
in their formation the tongue approaches the soft palate (#vēlum
palātī#).
45. #o# and #u# require a rounding of the lips (#labia#); hence they are
called _labial vowels_. The same is true for #y#.
46. Comparing the vowels in English _keen_ and _kin_, it will be noted
that the passage between the tongue and the hard palate is narrower in
the former than in the latter case. The _ee_ in _keen_ is therefore said
to be a _narrow_ or _close_ vowel, while the _i_ in _kin_ is _wide_ or
_open_. See 41.