Semantic change is the evolution of word usage. Semantic narrowing is the shift in which words refer to a more specific class of items or objects or the process by which a word's meaning becomes less general than its earlier meaning. Semantic narrowing is the narrowing of meaning. This happens when a word with a general meaning is applied to something more specific. Semantic narrowing is the opposite of semantic widening. ()
The process by which semantic narrowing occurs is called specialization. Most languages undergo semantic narrowing over time. Most semantic narrowing occurs because a definition for a word is used more frequently compared to other definitions so the definition eventually evolves to a more specific one. Some factors that affect semantic narrowing are liguistic, psychological, sociocultural, and cultural/encyclopedic factors.
Specialization is a process by which the meaning of a word shifts from the general to the specific definition. It occurs when a word is used for a specific definition more often than the others so it eventually evolves over time to having a more specific meaning. 
- Meat - The word mete (in Old English) or meat originally meant "food." In present day the word now means "food in the form of animal flesh."
- Skyline - The word skyline used to refer to any horizon, but now specifically means "a horizon decorated by skysrapers."
- Deer - The word deer originally meant "any four-legged beast," but now specifically means "an animal of the family Cervidae." ()
- Engine - The word engine meant "mechanical contrivance" (mostly of war or torture) but since the Industrial Revolution, Now means a mechanical sense of power.
- Accident - The word accident means "an unintended injurious or disastrous event." the word originally means any event, especially one that was unforseen.
- Girl - Originally meant a person of any gender, but now means a female person. ()
- Undertaker - Originally meant "one who undertakes to do anything," but now as come to mean "one who undertakes the special task of preparing bodies for burial."
- Disease - as can be seen by analyzing the word, once referred to any "discomfort," but now has the narrower meaning of "illness," that is, a particular type of discomfort.
- Verb- - The base originally meant "word"and still does in verbose and verbatim, but in hte case of verb, a particular type of word denoting action, it has narrowed its meaning.
- Diffident - once meant "not trusting," and Milton speaks of "diffedence of God"; but now it has acquired the more specific meaning of not trusting oneself, lacking self-confidence.
- Vest- - The base as a Latin word referred to any garment; now, however, vest is applied to a special type of clothing.()
- ↑ http://grammar.about.com/od/rs/g/semnarrterm.htm
- ↑ English Words from Latin and Greek Elements by Donald M. Ayers 1986
- ↑ http://thelousylinguist.blogspot.com/2008/11/semantic-narrowing.html
- ↑ http://www.westga.edu/~dnewton/engl2000/dialect_levels.html
- ↑ http://www.uni-due.de/SHE/Fowl_to_Bird.gif
Morphological: Folk etymology