a) Semantically morphemes fall into two classes: root-morphemes and non-root or affixation al morphemes. Roots and affixes make two distinct classes of morphemes due to the different roles they play in word-structure.
U-h e root-morpheme is the lexical nucleus of a word, it has an individual lexical meaning shared by no other morpheme of the language. The root-morpheme is isolated as the morpheme common to a set of words making up a word-cluster, for example the morpheme teach-in to teach, teacher, teaching, theory in theory, theorist, theoretical, etc. Non-root morphemes include inflectional morphemes or inflections and affixational morphemes or affixes. Inflections carry only grammatical meaning and are thus relevant only for the formation of word-forms, whereas affixes are relevant for building various types of stems-the part of a word that remains unchanged throughout its paradigm.
Lexicology is concerned only with affixational morphemes. A f f i x e s are classified into prefixes and s u f f i xes: a prefix precedes the root-morpheme, a suffix follows it. Affixes besides the meaning proper to root-morphemes possess the part-of-speech meaning and a generalized lexical meaning.
b) Structurally morphemes fall into three types: free morphemes, bound morphemes, semi-free (s e m i -bound) morphemes. A free morpheme is defined as one that coincides with the stem 2 or a word-form. A great many root-morphemes are free morphemes, for example, the root-morpheme friend — of the noun friendship is naturally qualified as a free morpheme because it coincides with one of
the forms of the noun friend.
A bound morpheme occurs only as a constituent part of a word. Affixes are, naturally, bound morphemes, for they always make part of a word, e.g. the suffixes -ness, -ship, -ize, etc., the prefixes un-, dis-, de-, etc. (e.g. readiness, comradeship, to activize; unnatural, to displease, to decipher). Semi-bound (semi-free) morphemes1 are morphemes that can function in a morphemic sequence both as an affix and as a free morpheme. For example, the morpheme well and half on the one hand occur as free morphemes that coincide with the stem and the word-form in utterances like sleep well, half an hour, on the other hand they occur as bound morphemes in words like well-known, half-eaten, half-done.
Speaking of word-structure on the morphemic level two groups of morphemes should be specially mentioned. To the first group belong morphemes of Greek and Latin origin often called combining f o-r m s, e.g. telephone, telegraph, phonoscope, microscope, etc.
The morphemes tele-, graph-, scope-, micro-, phone- are characterized by a definite lexical meaning and peculiar stylistic reference: tele- means ‘far’, graph- means ‘writing’, scope-‘seeing’, micro- implies smallness, phone- means ‘sound.’ Comparing words with tele- as their first constituent, such as telegraph, telephone, telegram one may conclude that tele- is a prefix and graph-, phone-, gram-are root-morphemes.
On the other hand, words like phonograph, seismograph, autograph may create the impression that the second morpheme graph is a suffix and the first-a root-morpheme_. This undoubtedly would lead to the absurd conclusion that words of this group contain no root-morpheme and are composed of a suffix and a prefix. Therefore, there is only one’ solution to this problem; these morphemes are all bound root-morphemes of a special kind and such words belong to words made up of bound roots.
The second group embraces morphemes occupying a kind of intermediate position, morphemes that are changing their class membership. The root-morpheme man- found in numerous words like postman [postmen], fisherman, gentleman in comparison with the same root used in the words man-made and man-servant is, as is well-known, pronounced, differently, the [ae] of the root-morpheme becomes [a] and sometimes disappears altogether. / we still recognize the identity of [man] in postman, cabman in man-made, man-servant^ we can hardly regard [man] as having completely lost the status of a root-morpheme?) It follows from all this that the morpheme -man as the last component may be qualified as semi-free.