1. Lecture 7 Summary Survey of English morphology
Morphology is the study of the way the words are built up from smaller meaning-bearing units called morphemes. Morphemes are defined as the minimum meaning-bearing units in a language.
Previously we learned how to accommodate both ‘cat’ and its plural form ‘cats’ in a regexp. But, how can we represent words such as ‘geese’, ‘foxes’ etc. which are also plural forms but do not follow the ‘cat  cats’ conversion rule? Morphological parsing is required for such a task.
The words such as ‘foxes’ are broken down into a stem and an affix. The stem is the root word while the affix is the extension added to the stem to represent either a different form of the same class or a whole new class.
In English, morphology can be broadly classified into two types:
Inflectional morphology: It is the combination of a word stem with a grammatical morpheme which results in a word of the same class as the original stem. In English infliction is simple, only nouns, verbs, and sometimes adjectives can be inflicted. Eg. catcats, mousemice, walkwalking etc.
Derivational morphology: It is the combination of a word stem with a grammatical morpheme which results in a word of a different class. In english it is very hard to predict the meaning of the stem from the derived structure. Eg. appointappointee, clueclueless, killkiller etc.