Homonymy
In linguistics, a homonym is, in the strict sense, one of a group of words that share the same phonological or morphological shape but have different meanings.[1] Homonyms are unrelated sense of the same phonological word. In other words, homonyms may have identical pronunciation but do not share common semantic features. Very often, they may have different written forms as well.

Contents
· 1 Etymology
· 2 Related terms
· 3 Further examples
· 4 Homonymy and polysemy
· 5 References
Etymology
The word homonym comes from the Greek ὁμώνυμος (homonumos), meaning "having the same name",[2] which is the conjunction of ὁμός (homos), meaning "common, same"[3] and ὄνομα (onoma) meaning "name".[4] Thus, it refers to two or more distinct concepts sharing the "same name" or signifier. Note: for the h sound, see rough breathing and smooth breathing.

Related Terms
Homographs refer to words which are written in the same way but differ in meaning and sometimes in pronunciation or derivation, e.g.
lead' /liːd/ v. 1.Cause (a person or animal) to go with one by holding them by the hand, a halter, a rope, etc., while moving forward 2. Show (someone or something) the way to a destination by going in front of or beside them 3. Be a reason or motive for (someone)
lead''/led/ n. 1.a heavy, soft, grayish metal 2. anything made of this metal, as a weight lowered on a line to find out deep water is 3.bullets

Homophones are words with identical pronunciation but with different spellings and meanings. Examples include:
knew vs. new
knot vs. not
be vs. bee

Homonyms can also be divided into full homonyms (like bank, punch), where all of the lexeme’s associated word forms are identical in pronunciation or spelling, and partial homonyms (like find, found), where part of their word forms is identical.

Further Examples
Schopenhauer suggests:

"You are not yet initiated into the mysteries of the Kantian philosophy."
..."Oh, if it's mysteries you're talking of, I'll have nothing to do with them."
I condemned the principle involved in the word honour as a foolish one; for, according to it, a man loses his honour by receiving an insult, which he cannot wipe out unless he replies with a still greater insult, or by shedding his adversary's blood or his own. I contended that a man's true honour cannot be outraged by what he suffers, but only and alone by what he does; for there is no saying what may befall any one of us. My opponent immediately attacked the reason I had given, and triumphantly proved to me that when a tradesman was falsely accused of misrepresentation, dishonesty, or neglect in his business, it was an attack upon his honour, which in this case was outraged solely by what he suffered, and that he could only retrieve it by punishing his aggressor and making him retract.
Here, by a homonymy, he was foisting civic honour, which is otherwise called good name, and which may be outraged by libel and slander, on to the conception of knightly honour, also called point d'honneur, which may be outraged by insult. And since an attack on the former cannot be disregarded, but must be repelled by public disproof, so, with the same justification, an attack on the latter must not be disregarded either, but it must be defeated by still greater insult and a duel. Here we have a confusion of two essentially different things through the homonymy in the word honour, and a consequent alteration of the point in dispute.

Homonymy and Polysemy
There is an extensive doubtful area between the concepts of polysemy and homonymy. A word like "walk" is polysemous (went walking, went for a walk, walk the dog, Hill Walk Drive), while a word like "bank" is homonymous between at least "bank" for money and the "bank" of a river.
The coexistence of several meanings in one word, which is extremely common, as stated earlier, is called polysemy. Some words develop a whole family of meanings, each new meaning often forming yet another starting point for more definitions.
If in a good dictionary you were to look up such words as "natural, good, loose, free", and "real"; you would be surprised at the number of meanings listed.

Being able to distinguish between polysemy words and homonym words is not easy.

Dictionaries treat cases of multiple meanings either as polysemy or as homonymy, but in fact it is not always easy to decide which one we are dealing with, and dictionaries sometimes differ in their decisions.
Are "table" (furniture) and "table" (arrangement of data) two different words, or the same word with two meanings? Dictionaries usually go for the latter solution, on the grounds of a shared etymology.
On the other hand, "a pupil" (in school) and the "pupil" (of the eye) are usually listed as different words; although in fact they have the same historical origin.

Reference
1. homonym, Random House Unabridged Dictionary at dictionary.com
2.Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
3.Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
4.Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
5.Yang Xinzhang, English Lexic0logy: A Coursebook