Word-structure (word-building), which studies the elements the word consists of (morphemes: roots, affixes) and the patterns according to which words are built: affixation, composition, conversion, shortening, sound imitation, etc.
Properties of roots:
-main part of word
-must be at least one in a word
-can occur independently (free roots)--although bound roots, particularly classical, occur
-tend to have richer, more specific semantic content
-position is relatively free with respect to other roots (cf. photograph vs. telephoto)
Properties of affixes:
-subordinate part of word
-not necessarily present--some words occur without any
-multiple affixes can occur in a word (e.g. in-divis-abil-ity)
-are dependent (bound) elements (where independent form found, generally to some degree dissociated from the bound version)
-have more "schematic" (non-specific) content; often grammar-like function
-can either precede or follow their roots (prefixes and suffixes,respectively)
-position for a given affix with respect to root is fixed
Conversion, one of the principal ways of forming words in Modern English, is highly productive in replenishing the English word-stock with new words. The term “conversion” refers to the numerous cases of phonetic identity of two words belonging to different parts of speech. As a rule we deal with root-words, although there are exceptions. This phenomenon may be illustrated by the following cases: work – to work, love – to love
Thus, derivation and compounding represent addition as suffixes and free stems respectively are added to the underlying form. S h o r t e n i n g , on the other hand, may be represented as subtraction, in which part of the original word is taken away.