English: Homonyms, Homophones and homographs.

Homophone:  
which have the same pronunciation as each other but different spellings and meanings. 
Ate - eight, Pour - paw, there - their, four - for

Homonym:  
Words that are written (spelt) and pronounced in the same way  

but different meanings and origins

Fluke can mean:
A fish, and a flatworm.
The end parts of an anchor.
The fins on a whale's tail.
A stroke of luck.
Other examples are:   quail (cower) and quail (bird) or fair (appearance), fair (county fair) and fair (reasonable).

Homograph:
Two words that written in the same way that have different meanings and are pronounced differently. i.e. sow (plant) sow (female pig), lead (Metal), Lead (guide)

Others are
accept - take in                except - other than  

ad - advertisement          add - join, combine

advice - guidance           advise - recommend

aid - assist, assistance   aide - one who gives assistance

ail - to suffer poor health    ale - a beverage

air - atmosphere              heir - one who inherits property

aisle - a passage              I'll - contraction of I willisle - island

allusion - an indirect reference     illusion - false appearance

altar - table in a church                  alter - to change

ate - past tense of eat     eight - the number 8

bail - to clear water        bail - release of a prisoner       bale - a large bundle

band - a ring, something that binds              band - a group            banned - prohibited

bare - uncovered              bear - large animal             bear - support, yield

bases - starting pointsbases - four stations on a baseball field              basis - a basic principlebeat - to strike, overcome

beat - exhausted              beet - a plant with red rootsblew - past tense of blow

blue - the color                 bread - baked food item           bred - produced

buy - purchase                 by - near, through           bye - goodbye

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Note that some dictionaries and textbooks define and distinguish these three terms in different ways.

Source:  Book:  Oxford A-Z Grammar and Punctuation, http://www.firstschoolyears.com/literacy/word/other/homonyms/homonyms.htm
http://grammar.about.com/od/words/a/HomonymChart.htm
http://en.wikipedia.org/wiki/Homonym
http://www.editingandwritingservices.com/homonyms.html