The English Alphabet consists of twenty-six letters, viz.:
a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z.
Letters are divided into VOWELS and CONSONANTS.
The Vowels are those letters which can be perfectly sounded without the
aid of any other letter. The vowels are a, e, i, o, u, w, and y.
The vowel sounds of w and y are the same as those of u and i. A, e, and o
are always vowels. I, u, w, and y are sometimes consonants.
A Diphthong is the union of two vowels in one sound. When both vowels are
sounded, the diphthong is called PROPER, because then it is really a
DIPHTHONG, or double sound; that is, the sounds of the vowels unite; as,
oi in oil; ou in sound.
When only one of the vowels is sounded, the diphthong is called IMPROPER,
because then, as one of the vowels is silent, it is not properly a
DIPHTHONG, though it takes that name; as, oa in boat, ui in suit, where a
and i are silent.
The following diphthongs are in common use, viz.: oi, oy, ou, ow, ae, ai,
au, aw, ay, ea, ei, eo, eu, ew, ey, ia, ie, oa, oe, ua, ue, ui; as in
toil, boy, round, plow, seal, coal, head, sail, say, aught, yeoman. Of
these, oi, oy, ou, and ow are generally proper diphthongs; though
sometimes ou and ow are improper, as in famous, where o is silent, and in
slow, where w is silent.
A Triphthong is the union of three vowels in one syllable; as, eau in
beau, iew in view. The triphthong is properly a union of letters, not
sounds.