Preffix is a derivational morpheme standing before root and modifying meaning. It may serve to distinguish one part of speech from another. E.g.: earth-unearth.

Affixation

Productive - which take part in deriving new words in this particular period of language development. E.g.: Noun: -er ,-ing, -ness, -ist. Adjectives: -y, -ish, -ed, -able. Adverb: -ly. Verb: -ize/ise, --ate. Prefixes: un-, re-, dis-.

Partially - productive - the derivatives build by means of partially - productive affixes. They are limited in coining new words. They are rare. E.g.: Noun: -lin, -ese, -ster, -ie,- let. Prefixes: be-, mis-, dis-, co-.

Non- productive - are those that do not take part in deriving new words in modern English. E.g.: Noun: -th, -hood, -ship-, dom. Adjective: -ly, -some, -ous, -ful. Verb: -en, -fy. Adverb: -wards.

Dead - have undergone the process of archaization during the historical development of the language so they have merged with the root and now can not be recognized as word-building morphemes.

Valency is essential feature of affixes, their combining power. The possibility of a particular stem taking a particular affix depends on phonomorphological, morphological and semantic factors. E.g: suffixes -ance/ence occur only after b,t,d,dz,v,l.(insistence), but not after s,z (conservation).

Allomorph is a term, used to denote elements of a group, whose members constitute a structural unit of the language. They don't differ in meaning but show a slight difference in sound form. An allomorph is a positional variant of a morpheme occurring in a specific environment and characterized by complementary distribution (when 2 linguistic variants can't appear in the same environment).

Conversion

Conversion is process of coining a new word with different distribution characteristics without adding any derivative element, so that the basic form of the original and the basic form of derived word are homonymous. E.g.: to find - a find, печь - печь.

Reasons:

1. The analytical structure of modern English.

2. The simplicity of paradigms of English parts of speech, that is the absence of morphological elements serves as classifying signals. E.g.: finger (noun) - linger (verb) - longer (adjective) - longer (adverb).

3. A great number of one-syllable words.

Substantivation

It is such case when word with an adjective stem has the paradigm of a noun. E.g.: a private, the private uniform, a group of privates. It is also the result of ellipsis when a word combination with a semantically strong attribute loses its semantically weak noun. The degree can be different. There exist complete substantivation (e.g.: a criminal, criminals, a criminal mistake, criminals'); partial (substantivised adjective or participle denotes a group or a class of people. E.g.: the blind, the poor, the dead, the rich. These words undergo no morphological changes; so they are used with the definite article, possess a collective mean.).

Composition

Composition is a type of word building in which new words are produced by combining 2 or more stems. There are 3 aspects of composition: structural, semantic, theoretical.

Structural Aspect

3 types of compounds:

1. Neutral - the process of compounding takes place without any linking element by a mere juxtaposition of 2 stems (armchair, breakwater). Neutral compounds are subdivided into: simple (consist of simple affixless stem); derived (have affixes in at least one constituate: blue-eyed, newcomer); contracted (have a shortened stem in their structure: T-shirt, FBI-agent); compounds where at least one of the constituance is a compound stem (wastepaper-basket, cornflower-blue).

2. Morphological - 2 compounding stems are combined by a linking vowel or consonant (statesman, handicraft).

3. Syntactic - the components represent segments of speech preserving in their structure numerous traces of sintagmatic relations (do-all, free-for-all, good-for-nothing, son-in-low.).