Polysemy

A polyseme

  is a word or phrase with different, but related senses. Since the test for polysemy is the vague concept of relatedness, judgments of polysemy can be difficult to make. Because applying pre-existing words to new situations is a natural process of language change, looking at words' etymology is helpful in determining polysemy but not the only solution; as words become lost in etymology, what once was a useful distinction of meaning may no longer be so.

In vertical polysemy a word refers to a member of a subcategory (e.g., 'dog' for 'male dog').^[4] A closely related idea is metonym, in which a word with one original meaning is used to refer to something else connected to it.

Examples

Man

1.      The human species (i.e., man vs. animal)

2.      Males of the human species (i.e., man vs. woman)

3.      Adult males of the human species (i.e., man vs. boy)

This example shows the specific polysemy where the same word is used at different levels of a taxonomy. Example 1 contains 2, and 2 contains 3.

Mole

1.      a small burrowing mammal

2.      consequently, there are several different entities called moles (see the Mole disambiguation page). Although these refer to different things, their names derive from 1. :e.g. A Mole burrows for information hoping to go undetected.

Bank

1.      a financial institution

2.      the building where a financial institution offers services

3.      a synonym for 'rely upon' (e.g. "I'm your friend, you can bank on me"). It is different, but related, as it derives from the theme of security initiated by 1.

However: a river bank is a homonym to 1 and 2, as they do not share etymologies. It is a completely different meaning.^[15] River bed, though, is polysemous with the beds on which people sleep.

Book

1.      a bound collection of pages

Newspaper

1.      a company that publishes written news.

2.      a single physical item published by the company.

 

http://grammar.about.com/od/fh/g/Homonymy.htm