In studying the English language, morphology is relatively simple. We have endings such as -ing, -s, and -ed, which are applied to verbs; endings such as -s and -es, which are applied to nouns; we also have the ending -ly, which usually indicates that a word is an adverb.
We also have prefixes such as anti-, non-, un-, and in-, which tend to indicate negation, or opposition.
We also have a number of other prefixes and suffixes that provide a variety of semantic and syntactic information.
In practice, however, morphologic analysis for the English language is not terribly complex, particularly when compared with agglutinative languages such as German, which tend to combine words together into single words to indicate combinations of meaning.
Morphologic analysis is mainly useful in natural language processing for identifying parts of speech (nouns, verbs, etc.) and for identifying which words belong together.
In English, word order tends to provide more of this information than morphology, however. In languages such as Latin, word order was almost entirely superficial, and the morphology was extremely important. Languages such as French, Italian, and Spanish lie somewhere between these two extremes.
As we will see in the following sections, being able to identify the part of speech for each word is essential to understanding a sentence. This can partly be achieved by simply looking up each word in a dictionary, which might contain for example the following entries: (swims, verb, present, singular, third person) (swimmer, noun, singular) (swim, verb, present, singular, first and second persons) (swim, verb, present plural, first, second, and third persons) (swimming, participle) (swimmingly, adverb) (swam, verb, past) Clearly, a complete dictionary of this kind would be unfeasibly large.
A more practical approach is to include information about standard endings, such as: (-ly, adverb) (-ed, verb, past) (-s, noun, plural) This works fine for regular verbs, such as walk, but for all natural languages there are large numbers of irregular verbs, which do not follow these rules. Verbs such as to be and to do are particularly difficult in English as they do not seem to follow any morphologic rules.
The most sensible approach to morphologic analysis is thus to include a set of rules that work for most regular words and then a list of irregular words. For a system that was designed to converse on any subject, this second list would be extremely long. Most natural language systems currently are designed to discuss fairly limited domains and so do not need to include over-large look-up tables.
In most natural languages, as well as the problem posed by the fact that word order tends to have more importance than morphology, there is also the difficulty of ambiguity at a word level. This kind of ambiguity can be seen in particular in words such as trains, which could be a plural noun or a singular verb, and set, which can be a noun, verb, or adjective.
