y

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The 25th letter of the modern English alphabet.
2. n. Any of the speech sounds represented by the letter y.
3. n. The 25th in a series.
4. n. Something shaped like the letter Y.
5. The symbol for ordinate.

Century Dictionary and Cyclopedia

1. In electricity, the symbol for admittance, in alternating-current circuits. See admittance, 6.
2. [lowercase] An abbreviation of yard.
3. [lowercase or cap.] A corruption of the Anglo-Saxon character , equivalent to th, giving ye for the or thee; and, by contraction, ym for them; yn for then; yr for their; ys for this; yt for that. See def. 1.
4. The twenty-fifth letter in the English alphabet. It has both a vowel and a consonant value. The character (as was pointed out under U) is the finally established Greek form of the sign added by the Greeks next after T (which had been the last Phenician letter) to express the oo(ö)-sound; U and V are other forms of it, which have kept more nearly their original place and value. As a Greek vowel, Y underwent a phonetic change which made of it the equivalent of the present French u, German ü, a rounded i, or a blending of the i- and u-sounds; and in the first century b. c. it was added by the Romans to their alphabet (which had till then ended with x) to express this sound in the Greek words borrowed into their language. With the same value it passed also into Anglo-Saxon use; but its sound gradually changed to that of a pure or unrounded i; and then its further development into a sign for both vowel and consonant is analogous with the partial differentiation of U or V and W (see W). It differs from w, the other character having the double value of vowel and consonant, in being not only exchanged with i in diphthongs and vowel-digraphs—as ai ay, ei ey, oi oy—but also commonly used by itself as the vowel of a syllable, as in by, deny, sylph, lying, taking the place of i both at the end of a word (since no proper English word except the pronoun I is allowed to end with i) and elsewhere, and constantly exchanging with i and ie in the different inflectional forms of the same words: as, pony, ponies; pretty, prettier; deny, denies, denied, denier; and so on. In Anglo-Saxon y properly expressed the mixed sound ii; but it early began to interchange with i, and in Middle English the two became convertible, y being often substituted for i as being more legible, and as affording, especially at the end of a word, an opportunity for a calligraphic flourish. Hence its present prevalence at the end of words, while in the inflected forms the older i is retained, families, the plural of familie, remaining beside family, the flourished spelling, without the original final e, of familie. As a vowel-sign, y is a superfluity in our alphabet, signifying nothing which would not be just as well signified by i. The consonant y is really a different letter, representing the Middle English ʒ, the Anglo-Saxon g. The value is that of a semivowel, related to the i-sounds (ĭ and ē) precisely as w is related to the u-sounds (u and oo or ö); if at all dwelt on or prolonged, it becomes an ĭ or ē. With this value it stands always before another vowel, as in yam, ye, yield, you, Yule. In very many words it is a matter of comparative indifference, and subject to constant variation in practice, whether an i before a vowel shall be pronounced as a vowel, making a separate syllable, or as y, combining into one syllable with its successor. In the respellings for pronunciation of this dictionary, such cases are often written with an i in the same syllable with the following vowel: examples are cor-dial, fo-lio, fa-shient, e-ras-tian. The semivowel y-sound is not only thus written with y and with i (sometimes also with e, as in the ending -ceous), but it is sounded without being written in a large class of words as the first element of what is called “long u” (that is, yoo: see U), as in use, union: and then, even when the oo (ö) part of the combination is reduced by slighting even to the neutral-vowel sound (u or u or ė), the y remains: hence, fig'yėr, not fig'ēr, for fig'ū r (fig'yör). In all these varieties of designation, the semi-vowel y-sound is a much rarer element than the w-sound in English utterance, making but $⅔$ of one per cent. of the latter, while the w is 2⅓ per cent. The character y in the archaic forms or abbreviations ye, yat, y, y, etc., is neither the Greek y nor the Anglo-Saxon y (ʒ), but a form of the Anglo-Saxon and Middle English p, now written th, and is to be pronounced, of course, as th.
5. As a symbol:
6. In chem., the symbol of yttrium.
7. In ornithology, in myological formulas, the symbol of the accessory semitendinosus.
8. In mathematics:
9. [lowercase] In algebra, the second of the variables or unknown quantities.
10. [lowercase] In analytical geometry, the symbol of the ordinate or other rectilinear point-coördinate.
11. In mechanics, the component of a force in the direction of the axis of y.
12. As a medieval Roman numeral, the symbol for 150, and with a line drawn above it (Y), 150,000.
13. [lowercase] An abbreviation of year.
14. n. Something resembling the letter Y in shape. Specificallymdash; A forked clamp for holding drills or other tools.
15. n. An old mode of writing the pronoun I.
16. n. See i-. For Middle English words with this prefix, see i-, or the form without the prefix.
17. n. A very common suffix used to form adjectives from nouns, and sometimes from verbs, such adjectives denoting ‘having,’ ‘covered with,’ ‘full of,’ etc., the thing expressed by the noun, as in stony, rocky, icy, watery, rainy, dewy, meaty, juicy, mealy, salty, peppery, powdery, flowery, spotty, speckly, etc. It may be used with almost any noun, but is found chiefly with monosyllablcs, while examples of its use with trisyllables are rare.
18. n. A diminutive suffix, appearing chiefly in childish names of animals, etc., as kitty, doggy, piggy, birdy, froggy, mousy, and similar names, or familiar forms of personal names, as Katy or Kitty (diminutive of Kate), Jenny, Hetty, Fanny, Willy, Johnny, Tommy, etc., such names being often spelled with -ie, as Willie, Davie, etc., a spelling common in Scotch use, and also in general use in names of girls, as Katie, Jennie, Hettie, Carrie, Lizzie, Nellie, Annie, etc. Such names coincide in terminal form with some feminine names not actually diminutive, as Mary, Lucy, Lily, formerly and sometimes still written Marie, Lucie, Lillie, etc. The diminutive termination is not used, except as above, in English literary speech, but it is common in Scotch, as in beastie, mannie, lassie, sometimes with a second diminutive suffix, as in lassiekie, etc.
19. n. A termination of nouns from the Latin or Greek, or of modern formation on the Latin or Greek model. Such nouns are or were originally abstract, but many are now concrete. Examples are family, innocency, homily, theory, geography, philosophy, philology, etc.; the list is innumerable. Besides words from the Latin and Greek, many other words have the termination -y, either after the analogy of the Latin and Greek termination, or from some other source. As the termination in such cases usually has no significance, and is therefore not used as formative within the meaning assigned to that word, such words, which are very numerous and intractable to classification, are here ignored.

Wiktionary

1. n. The twenty-fifth letter of the basic modern Latin alphabet.
2. n. metrology Symbol for the prefix yocto-.
3. n. close front rounded vowel
4. n. Denoting an item that is twenty-fifth in a list.
5. n. The twenty-fifth letter of the English alphabet, called wye and written in the Latin script.
6. abbr. Abbreviation of year.
7. abbr. UK, television Abbreviation of youth., usually followed by an age appropriate for the content so marked.
8. abbr. computing Abbreviation of yes.
9. abbr. slang, text messaging, Internet Abbreviation of why.?

GNU Webster's 1913

1. Y, the twenty-fifth letter of the English alphabet, at the beginning of a word or syllable, except when a prefix (see Y-), is usually a fricative vocal consonant; as a prefix, and usually in the middle or at the end of a syllable, it is a vowel. See Guide to Pronunciation, §§ 145, 178-9, 272.
2. n. One of the forked holders for supporting the telescope of a leveling instrument, or the axis of a theodolite; a wye.
3. n. A forked or bifurcated pipe fitting.
4. n. (Railroads) A portion of track consisting of two diverging tracks connected by a cross track.
5. pro. obsolete I.

WordNet 3.0

1. n. the 25th letter of the Roman alphabet
2. n. a silvery metallic element that is common in rare-earth minerals; used in magnesium and aluminum alloys