Where do derivational affixes like -ful and -less come from? Many affixes like these have come from full words (free morphemes) and gradually changed into affixes (bound morphemes). For example， in careful，beautiful，or wonderful，the suffix -fu/originates from the adjective full，which was first used in compounds such as mouthful，and spoonful. As a suffix，the form -ful has gradually acquired the more generalized and abstract meaning of“possessing some value to a very high degree”. The affix-ful is the opposite of -less，which goes back to Old English leas meaning “without”. Compare careful/careless，hope-ful/hopeless and merciful/merciless. The process whereby an independent word is shifted to the status of a grammatical element is called grammaticalization. Usually，in grammaticalization，words from major grammatical categories，such as nouns，verbs and adjectives become minor grammatical categories such as prepositions，adverbs and auxiliaries，which in turn may be further grammaticalized into affixes. Full words，with their own lexical content，thus become form words；and this categorial change tends to be accompanied by a reduction in phonological form and a“bleaching”of meaning. Therefore， grammaticalization is not only a syntactic change，but also a global change influencing the morphology， phonology and semantics.

A famous example in English is the transition of the lexical verb “go”into an auxiliary used to express the future tense. Compare the following examples (lingerer & Schmid，1996：255)：

（21）a. Susan's going to London next month.

b.She's going to London to work at our office.

c.She's going to work at our office.

d.You're going to like her.

e.You're gonna like her.

f.You gonna like her. (non-standard)

In these examples，the development starts out from the use of the word“go”as a verb of motion with a directional adverbial. This applies to (21a，21b) although (21b) has an adverbial of purpose. (21c) indicates the turning point. The directional adverbial is omitted，and now the meaning focuses on the subject's intention which is to be realized in the future. (21d) takes us one step further because the subject here is no longer an agent，but rather the experiencer of an attitude (the affection towards Susan). The meaning of“going to”is no longer intentional，but a kind of prediction based on the present situation. (21e，21 f) do not change the semantic meaning，but record the phonological changes which accompany the transition of“going to” into a grammatical form“gonna”.

Grammaticalization brings about typical changes in meanings and the distribution of forms. One of these is that，when a lexical form becomes a grammatical morpheme，the original form may remain as an autonomous element and undergo the same changes as other lexical items. As a result，the lexical and the grammatical forms coexist. This divergence has happened with the Old English adjective “ān” (one，a certain)，which was grammaticalized as the indefinite article but continued to exist in its original lexical form as ”one”(as well as in the affixed forms“any”“once”“alone”“lone”and “only”).

Another characteristic of grammaticalized forms is that the constraints on their grammatical uses tend to reflect their lexical histories. For example，the uses of the English auxiliary“Will” include not only predictive future-tense meanings (e.g. “It will rain tomorrow”)，but also willingness (e.g.“l will help you with the violin”)，and intention (e.g.“I’ll put them in the post today”)；both of the latter were common meanings of the verb “willan”in Old English. The development of a future-tense meaning occurred by way of encroachment on the earlier meanings，which left them as possible current uses.

Another typical outcome of grammaticalization is the development of different historical levels of nearly equivalent forms. As new ways of expressing functions appear，the older ones are often not discarded， but remain as alternatives. An obvious instance is the English past-tense system，in which the older technique involving a vowel change (e.g. “drive/drove”) exists side by side with the newer technique of suffixation (e.g. “cook/cooked”).

This revival of interest is attributable not only to the intrinsic value of grammaticalization for the study of the histories of individual languages，but to the profound questions which are raised by the terms of the study itself：What is grammar? What causes the change of language?

The language we use to express the world is based on our cognitive conceptual structures and the worldly experience from which they come from. Cognitive linguistics provides many new angles for our insight into language. Its significant position in linguistics is evident. It seems to give us hope that some unsolved problems in language studies may be solved in cognitive linguistics.