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. Some apparently unrelated words share a common historical origin, however, so etymology is not an infallible test for polysemy, and dictionary writers also often defer to speakers' intuitions to judge polysemy in cases where it contradicts etymology. English has many words which are polysemous. For example, the verb "to get" can mean "procure" (I'll get the drinks), "become" (she got scared), "understand" (I get it) etc.

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

1. A word is polysemous if it can be used to express di erent meanings. The diff erence between the meanings can be obvious or subtle.  
2. Two or more words are homonyms if they either sound the same (homophones), have the same spelling (homographs), or both, but do not have related meanings.
3. In other words, if you hear (or read) two words that sound (or are written) the same but are not identical in meaning, you need to decide if it's really two words (homonyms), or if it is one word used in two di fferent ways (polysemy). 

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)

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. River bed, though, is polysemous with the beds on which people sleep.

Book

1. a bound collection of pages
2. a text reproduced and distributed (thus, someone who has read the same text on a computer has read the same book as someone who had the actual paper volume)
3. to make an action or event a matter of record (e.g. "Unable to book a hotel room, a man sneaked into a nearby private residence where police arrested him and later booked him for unlawful entry.")

Newspaper

1. a company that publishes written news.
2. a single physical item published by the company.
3. the newspaper as an edited work in a specific format (e.g. "They changed the layout of the newspaper's front page").