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In linguistics, morphology is the study of word structure. While words are generally accepted as being the smallest units of syntax, it is clear that in most (if not all) languages, words can be related to other words by rules. For example, English speakers recognize that the words dog, dogs and dog-catcher are closely related. English speakers recognize these relations by virtue of the unconscious linguistic knowledge they have of the rules of word-formation processes in English. Therefore, these speakers intuit that dog is to dogs just as cat is to cats, or encyclopædia is to encyclopædias; similarly, dog is to dog-catcher as dish is to dishwasher. The rules comprehended by the speaker in each case reflect specific patterns (or regularities) in the way words are formed from smaller units and how those smaller units interact in speech. In this way, morphology is the branch of linguistics that studies such patterns of word-formation across and within languages, and attempts to explicate formal rules reflective of the knowledge of the speakers of those languages.
The history of morphological analysis dates back to the ancient Indian linguist Pāṇini who formulated the 3,959 rules of Sanskrit morphology in the text Aṣṭādhyāyī. The Graeco-Roman grammatical tradition also engaged in morphological analysis.
The term morphology was coined by August Schleicher in 1859: Für die Lehre von der Wortform wähle ich das Wort "Morphologie" ("for the science of word formation, I choose the term 'morphology'", Mémoires Acad. Impériale 7/1/7, 35). It derives from the Greek words μορφή ("form") and λόγος ("explanation, account").
Lexemes and word forms
The term "word" is ambiguous in common usage. To take up again the example of dog vs. dogs, there is one sense in which these two are the same "word" (they are both nouns that refer to the same kind of animal, differing only in number), and another sense in which they are different words (they can't generally be used in the same sentences without altering other words to fit; for example, the verbs is and are in The dog is happy and The dogs are happy).
The distinction between these two senses of "word" is arguably the most important one in morphology. The first sense of "word," the one in which dog and dogs are "the same word," is called lexeme. The second sense is called word-form. We thus say that dog and dogs are different forms of the same lexeme. Dog and dog-catcher, on the other hand, are different lexemes; for example, they refer to two different kinds of entities. The form of a word that is chosen conventionally to represent the canonical form of a word is called a lemma, or citation form.
Inflection vs. word-formation
Given the notion of a lexeme, it is possible to distinguish two kinds of morphological rules. Some morphological rules relate different forms of the same lexeme; while other rules relate two different lexemes. Rules of the first kind are called inflectional rules, while those of the second kind are called word-formation. The English plural, as illustrated by dog and dogs, is an inflectional rule; compounds like dog-catcher or dishwasher provide an example of a word-formation rule. Informally, word-formation rules form "new words" (that is, new lexemes), while inflection rules yield variant forms of the "same" word (lexeme).
There is a further distinction between two kinds of word-formation: derivation and compounding. Compounding is a process of word-formation that involves combining complete word-forms into a single compound form; dog-catcher is therefore a compound, because both dog and catcher are complete word-forms in their own right before the compounding process was applied, and are subsequently treated as one form. Derivation involves affixing bound (non-independent) forms to existing lexemes, whereby the addition of the affix derives a new lexeme. One example of derivation is clear in this case: the word independent is derived from the word dependent by prefixing it with the derivational prefix in-, while dependent itself is derived from dépendant, the French present participle of dépendre which means "to hang down" (and is also a cognate of the English verb depend).
The distinction between inflection and word-formation is not at all clear-cut. There are many examples where linguists fail to agree whether a given rule is inflection or word-formation. The next section will attempt to clarify this distinction.
Paradigms and morphosyntax
A paradigm is the complete set of related word-forms associated with a given lexeme. The familiar examples of paradigms are the conjugations of verbs, and the declensions of nouns. Accordingly, the word-forms of a lexeme may be arranged conveniently into tables, by classifying them according to shared inflectional categories such as tense, aspect, mood, number, gender or case. For example, the personal pronouns in English can be organized into tables, using the categories of person, number, gender and case.
The inflectional categories used to group word-forms into paradigms cannot be chosen arbitrarily; they must be grammatical categories that are relevant to stating the syntactic rules of the language. For example, person and number are grammatical categories that can be used to define paradigms in English, because English has grammatical agreement rules that require the verb in a sentence to appear in an inflectional form that matches the person and number of the subject. In other words, the syntactic rules of English care about the difference between dog and dogs, because the choice between these two forms determines which form of the verb is to be used. In contrast, however, no syntactic rule of English cares about the difference between dog and dog-catcher, or dependent and independent. The first two are just nouns, and the second two just adjectives, and they generally behave like any other noun or adjective behaves.
An important difference between inflection and word-formation is that inflected word-forms of lexemes are organized into paradigms, which are defined by the requirements of syntactic rules, whereas the rules of word-formation are not restricted by any corresponding requirements of syntax. Inflection is therefore said to be relevant to syntax, and word-formation not so. The part of morphology that covers the relationship between syntax and morphology is called morphosyntax, and it concerns itself with inflection and paradigms, but not with word-formation or compounding.
Allomorphy and morphophonology
In the exposition above, morphological rules are described as analogies between word-forms: dog is to dogs as cat is to cats, and as dish is to dishes. In this case, the analogy applies both to the form of the words and to their meaning: in each pair, the first word means "one of X", while the second "two or more of X", and the difference is always the plural form -s affixed to the second word, signaling the key distinction between singular and plural entities.
One of the largest sources of complexity in morphology is that this one-to-one correspondence between meaning and form scarcely applies to every case in the language. In English, we have word form pairs like ox/oxen, goose/geese, and sheep/sheep, where the difference between the singular and the plural is signaled in a way that departs from the regular pattern, or is not signaled at all. Even cases considered "regular", with the final -s, are not so simple; the -s in dogs is not pronounced the same way as the -s in cats, and in a plural like dishes, an "extra" vowel appears before the -s. These cases, where the same distinction is effected by alternative changes to the form of a word, are called allomorphy.
There are several kinds of allomorphy. One is pure allomorphy, where the allomorphs are just arbitrary. Other, more extreme cases of allomorphy are called suppletion, where two forms related by a morphological rule cannot be explained as being related on a phonological basis: for example, the past of go is went, which is a suppletive form.
On the other hand, other kinds of allomorphy are due to the interaction between morphology and phonology. Phonological rules constrain which sounds can appear next to each other in a language, and morphological rules, when applied blindly, would often violate phonological rules, by resulting in sound sequences that are prohibited in the language in question. For example, to form the plural of dish by simply appending an -s to the end of the word would result in the form *[dɪʃs], which is not permitted by the phonotactics of English. In order to "rescue" the word, a vowel sound is inserted between the root and the plural marker, and [dɪʃəz] results. This is an example of vowel epenthesis in English. Similar rules apply to the pronunciation of the -s in dogs and cats: it depends on the quality (voiced vs. unvoiced) of the final preceding phoneme.
Lexical morphology is the branch of morphology that deals with the lexicon, which, morphologically conceived, is the collection of lexemes in a language. As such, it concerns itself primarily with word-formation: derivation and compounding.
Models of morphology
There are three principal approaches to morphology, which each try to capture the distinctions above in different ways. These are,
- Morpheme-based morphology, which makes use of an Item-and-Arrangement approach.
- Lexeme-based morphology, which normally makes use of an Item-and-Process approach.
- Word-based morphology, which normally makes use of a Word-and-Paradigm approach.
Note that while the associations indicated between the concepts in each item in that list is very strong, it is not absolute.
In morpheme-based morphology, word-forms are analyzed as sequences of morphemes. A morpheme is defined as the minimal meaningful unit of a language. In a word like independently, we say that the morphemes are in-, depend, -ent, and ly; depend is the root and the other morphemes are, in this case, derivational affixes. In a word like dogs, we say that dog is the root, and that -s is an inflectional morpheme. This way of analyzing word-forms as if they were made of morphemes put after each other like beads on a string, is called Item-and-Arrangement.
The morpheme-based approach is the first one that beginners to morphology usually think of, and which laymen tend to find the most obvious. This is so to such an extent that very often beginners think that morphemes are an inevitable, fundamental notion of morphology, and many five-minute explanations of morphology are, in fact, five-minute explanations of morpheme-based morphology. This is, however, not so. The fundamental idea of morphology is that the words of a language are related to each other by different kinds of rules. Analyzing words as sequences of morphemes is a way of describing these relations, but is not the only way. In actual academic linguistics, morpheme-based morphology certainly has many adherents, but is by no means the dominant approach.
Applying a strictly morpheme-based model quickly leads to complications when one tries to analyze many forms of allomorphy. For example, the word dogs is easily broken into the root dog and the plural morpheme -s. The same analysis is straightforward for oxen, assuming the stem ox and a suppletive plural morpheme -en. How then would the same analysis "split up" the word geese into a root and a plural morpheme? In the same manner, how to split sheep?
Theorists wishing to maintain a strict morpheme-based approach often preserve the idea in cases like these by saying that geese is goose followed by a null morpheme (a morpheme that has no phonological content), and that the vowel change in the stem is a morphophonological rule. Also, morpheme-based analyses commonly posit null morphemes even in the absence of any allomorphy. For example, if the plural noun dogs is analyzed as a root dog followed by a plural morpheme -s, then one might analyze the singular dog as the root dog followed by a null morpheme for the singular.
Lexeme-based morphology is (usually) an Item-and-Process approach. Instead of analyzing a word-form as a set of morphemes arranged in sequence, a word-form is said to be the result of applying rules that alter a word-form or stem in order to produce a new one. An inflectional rule takes a stem, changes it as is required by the rule, and outputs a word-form; a derivational rule takes a stem, changes it as per its own requirements, and outputs a derived stem; a compounding rule takes word-forms, and similarly outputs a compound stem.
The Item-and-Process approach bypasses the difficulties inherent in the Item-and-Arrangement approaches. Faced with a plural like geese, one is not required to assume a null morpheme: while the plural of dog is formed by affixing -s, the plural of goose is formed simply by altering the vowel in the stem.
Word-based morphology is a (usually) Word-and-Paradigm approach. This theory takes paradigms as a central notion. Instead of stating rules to combine morphemes into word-forms, or to generate word-forms from stems, word-based morphology states generalizations that hold between the forms of inflectional paradigms. The major point behind this approach is that many such generalizations are hard to state with either of the other approaches. The examples are usually drawn from fusional languages, where a given "piece" of a word, which a morpheme-based theory would call an inflectional morpheme, corresponds to a combination of grammatical categories, for example, "third person plural." Morpheme-based theories usually have no problems with this situation, since one just says that a given morpheme has two categories. Item-and-Process theories, on the other hand, often break down in cases like these, because they all too often assume that there will be two separate rules here, one for third person, and the other for plural, but the distinction between them turns out to be artificial. Word-and-Paradigm approaches treat these as whole words that are related to each other by analogical rules. Words can be categorized based on the pattern they fit into. This applies both to existing words and to new ones. Application of a pattern different than the one that has been used historically can give rise to a new word, such as older replacing elder (where older follows the normal pattern of adjectival superlatives) and cows replacing kine (where cows fits the regular pattern of plural formation). While a Word-and-Paradigm approach can explain this easily, other approaches have difficulty with phenomena such as this.
In the 19th century, philologists devised a now classic classification of languages according to their morphology. According to this typology, some languages are isolating, and have little to no morphology; others are agglutinative, and their words tend to have lots of easily-separable morphemes; while others yet are fusional, because their inflectional morphemes are said to be "fused" together. The classic example of an isolating language is Chinese; the classic example of an agglutinative language is Turkish; both Latin and Greek are classic examples of fusional languages.
Considering the variability of the world's languages, it becomes clear that this classification is not at all clear-cut, and many languages do not neatly fit any one of these types. However, examined against the light of the three general models of morphology described above, it is also clear that the classification is very much biased towards a morpheme-based conception of morphology. It makes direct use of the notion of morpheme in the definition of agglutinative and fusional languages. It describes the latter as having separate morphemes "fused" together (which often does correspond to the history of the language, but not to its synchronic reality).
The three models of morphology stem from attempts to analyze languages that more or less match different categories in this typology. The Item-and-Arrangement approach fits very naturally with agglutinative languages; while the Item-and-Process and Word-and-Paradigm approaches usually address fusional languages.
The reader should also note that the classical typology also mostly applies to inflectional morphology. There is very little fusion going on with word-formation. Languages may be classified as synthetic or analytic in their word formation, depending on the preferred way of expressing notions that are not inflectional: either by using word-formation (synthetic), or by using syntactic phrases (analytic).
- ↑ The existence of words like appendix and pending in English does not mean that the English word depend is analyzed into a derivational prefix de- and a root pend. While all those were indeed once related to each other by morphological rules, this was so only in Latin, not in English. English borrowed the words from French and Latin, but not the morphological rules that allowed Latin speakers to combine de- and the verb pendere 'to hang' into the derivative dependere.
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