The classification according to the part of speech.

2) according to lexico-grammatical character of the stem.

3) semantic classification.

It is quite relative, but there are 8 main groups:

Classification of prefixes

Both the simple word and its prefixed derivative mostly belong to the same part of speech: e.g. the prefix mis - when added to verbs, conveys the meaning 'wrongly', 'badly', behave - misbehave, pronounce - mispronounce. There may be other cases where the semantic rela­tionship is slightly different but the general lexico-grammatical meaning remains: giving - misgiving

To some extent the semantic effect of a prefix may be called adverbial because it modifies the idea of manner, time, place, degree and so on.

The prefixes pre - and post - refer to time. E.g. historic - prehisto­ric, pay - prepray, view - preview.

The prefixes in, a,ab - modify the root for place: e.g. income, abduct.

Several prefixes serve to modify the meaning of the stem for degree. The examples are out, over - and under -.

The prefix out- means 'in a manner that surpasses': outlive - “to live longer”, outnumber – “to exceed in number”.

The group of negative prefixes is so numerous that some scholars even find it convenient to classify prefixes into negative and non-negative ones. They are: de-, dis-, in-,im,-il-, ir-, un.

The prefix de - occurs in many neologisms, such decentralize, deconta­minate etc.

The general idea of negation is expressed by dis: Agree - disagree 'not to agree', appear - disappear (disappear is the reverse of appear).

Non - is often used in abstract verbal nouns such as noninterference or nonresistance.

The most frequent by far is the prefix un; it may convey two different meanings.

1) Simple negation, when attached to adjective stems or to participles: happy-unhappy. It is immaterial whether the stem is native or borrowed, as the suffix un - readily combines with both groups. 2) The meaning is different when un- is used with verbal stems. In that case it shows action contrary to that of the simple word: bind - unbind, do – undo.

A very frequent prefix with a great combining power is re. It denotes repetition of the action expressed by the stem, e.g. to rearrange, to recast.

The majority of prefixes affect only the lexical meaning of words but there are some important cases where prefixes serve to form words belon­ging to different parts of speech as compared with the original word.

These are in the first place the verb-forming prefixes be - and en. Be - forms transitive verbs with adjective and noun stems and changes intransitive verbs into transitive ones, e.g. to belittle – “to make little”; to benumb – “to make numb”;.

The prefix en-em - is used to form verbs from noun stems with the meaning “put (the object) into”, or on e.g. to embed, to encamp and to form verbs with adjective and noun stems with the meaning “to bring into such condition or state”, as in to enable, to enslave. The prefix a - is the characteristic feature of the words belonging to statives: aboard, afraid, asleep, awake, etc.

The prefixes pre; post-, non-, anti- and some other Romanic and Greek prefixes very productive in present-day English serve to form adjec­tives retaining at the same time a very clearcut lexical meaning, e.g. anti-war, pre-war, post-war, non-party, etc.