Word structure
In morphology, word structure is described in terms of roots and affixes
Simple words consist one morpheme – the root
fun, go, danger
Complex words consist more that one morpheme – the root + affix(es)
funny, goes, endanger
Languages have three principal ways of extending their vocabulary:
invention of entirely new words
borrowing from other languages
formation of new words from already existing words and word parts
Invention of new words
This is very rare
It is much easier for languages to either incorporate new meanings to existing words or borrow from another language than to make new words from scratch
Borrowing from other languages
Most language users have borrowed words from other languages and incorporated them into their own.
Deriving new words
Some ways in which new words are built from existing ones, in English are:
compounding
Shortening
Acronyms
blends
back formation
functional shift or conversion
semantic shift (metaphorical Extension)
Compounding
Compounding is a very common form of creating new words in English. It is the combination of two words to form one.
e.g.
waterbed
Shortening
Shortenings of various sorts are a popular means of multiplying the words of a language.
e.g.
feds –  federal agents
Acronyms
These are words formed by joining the initial letters of an expression and pronouncing them as a word.
e.g.
FIFA
Blends
Blends are words created by combining parts of existing words.
e.g.
motel – motor + hotel
Backformation
Words that are formed (again) from derivations of existing words to include a different meaning.
e.g.
computer
originally formed by adding –er to (existing) verb compute (calculate using a mathematical function) then, the computer was invented machine that computed (in the mathematical sense), however now compute has been back-formed carrying the meaning ‘to use a computer’
Functional Shift
In some languages (e.g. English) words belonging to one lexical category get converted to another lexical category without any overt markings on the words itself.
e.g.
local (noun; adjective)
Semantic Shift
This occurs when existing words take on new meaning by shrinking or extending their domain or usage.
When a word undergoes a functional shift in meaning, they do not replace the old one, but instead extend their range of application.
e.g.
Computer users today use a mouse and bookmark an Internet address.
Semantic Shift
Functional shifts create metaphors, then the metaphorical use of the words often leads to new meanings that come to seem perfectly natural and hence all but lose their metaphorical content.
