Some of the ways of forming words in present-day English can be resorted to for the creation of new words whenever the occasion demands ? these are called pr?du?tive ways of forming words, other ways of forming words cannot now produce new words, and these are commonly termed non-productive or unproductive. For instance, affixation has been a productive way of forming words ever since the Old English period; on the other hand, sound-interchange must have been at one time a word-building means but in Modern English, as has been mentioned above, its function is actually only to distinguish between different classes and forms of words.
It follows that productivity of word-building ways, individual derivational patterns and derivational affixes is understood as their ability of making new words which all who speak English find no difficulty in understanding, in particular their ability to create what are called ? ?-casional words or nonce-w?rds.2 The term suggests that a speaker coins such words when he needs them; if on another occasion the same word is needed again, he coins it afresh. Nonce-words are built from familiar language material after familiar patterns.3 Needless to say dictionaries do not as a rule record occasional words. The following words may serve as illustration: (his) collarless(appearance), a lungful(of smoke), a Dickensish(office), to unlearn(the rules), etc.
The delimitation between productive and non-productive ways and means of word-formation as stated above is not, however, accepted by all linguists without reserve. Some linguists consider it necessary to define the term productivity of a word-building means more accurately. They hold the view that productive ways and means of word-formation are only those that can be used for the formation of an unlimited number of new words in the modern language, i.e. such means that ?know no bounds" and easily form occasional words. This divergence of opinion is responsible for the difference in the lists of derivational affixes considered productive in various books on English Lexicology.
Recent investigations seem to prove however that productivity of derivational means is relative in many respects. Moreover there are no absolutely productive means; derivational patterns and derivational affixes possess different degrees of productivity. Therefore it is important that conditions favouring productivity and the degree of productivity of aparticular pattern or affix should be established. All derivational patterns experience both structural and semantic constraints. The fewer are the constraints the higher is the degree of productivity, the greater is the number of new words built on it. The two general constraints imposed on all derivational patterns are ? the part of speech in which the pattern functions and the meaning attached to it which conveys the regular semantic correlation between the two classes of words. It follows that each part of speech is characterised by a set of productive derivational patterns peculiar to it. Three degrees of productivity are distinguished for derivational patterns and individual derivational affixes: l) highly-productive, 2) productive or semi-productive and 3) non-productive.
Productivity of derivational patterns and affixes should not be identified with frequency of occurrence in speech, although there may be some interrelation between them. Frequency of occurrence is characterised by the fact that a great number of words containing a given derivational affix are often used in speech, in particular in various texts. Productivity is characterised by the ability of a given suffix to make new words.
In linguistic literature there is another interpretation of derivational productivity based on a quantitative approach.1 A derivational pattern or a derivational affix are qualified as productive provided there are in the word-stock dozens and hundreds of derived words built on the pattern or with the help of the suffix in question. Thus interpreted, derivational productivity is distinguished from word-formation activity by which is meant the ability of an affix to produce new words, in particular occasional words or nonce-words. To give a few illustrations. The agent suffix -er is to be qualified both as a productive and as an active suffix: on the one hand, the English word-stock possesses hundreds of nouns containing this suffix (e.g. driver, reaper, teacher, speaker,etc.), on the other hand, the suffix -erin the pattern v+-er -> N is freely used to coin an unlimited number of nonce-words denoting active agents (e.g., interrupter, respecter, laugher, breakfaster,etc.).
The adjective suffix -fulis described as a productive but not as an active one, for there are hundreds of adjectives with this suffix (e.g. beautiful, hopeful, useful,etc.), but no new words seem to be built with its help.
For obvious reasons, the noun-suffix -thin terms of this approach is to be regarded both as a non-productive and a non-active one.