The Use of Word Stems in English

In English grammar and morphology, a stem is the form of a word before any inflectional affixes are added. In English, most stems also qualify as words. The term base is commonly used by linguists to refer to any stem (or root) to which an affix is attached. Identifying a Stem A stem may consist of a single root, of two roots forming a compound stem, or of a root (or stem) and one or more derivational affixes forming a derived stem.(R. M. W. Dixon, The Languages of Australia. Cambridge University Press, 2010) Combining Stems The three main morphological processes are compounding, affixation, and conversion. Compounding involves adding two stems together, as in . . . window-sill--or blackbird, daydream, and so on. . . . For the most part, affixes attach to free stems, i.e., stems that can stand alone as a word. Examples are to be found, however, where an affix is added to a bound stem--compare perishable, where perish is free, with durable, where dur is bound, or unkind, where kind is free, with unbeknown, where beknown is bound. . . . Stem Conversion Conversion is where a stem is derived without any change in form from one belonging to a different class. For example, the verb bottle (I must bottle some plums) is derived by conversion from the noun bottle, while the noun catch (That was a fine catch) is converted from the verb.(Rodney D. Huddleston,  English Grammar: An Outline. Cambridge University Press, 1988) The Difference Between a Base and a Stem Base is the core of a word, that part of the word which is essential for looking up its meaning in the dictionary; stem is either the base by itself or the base plus another morpheme to which other morphemes can be added. [For example,] vary is both a base and a stem; when an affix is attached the base/stem is called a stem only. Other affixes can now be attached.(Bernard ODwyer,  Modern English Structures: Form, Function, and Position. Broadview, 2000) The Difference Between a Root and a Stem The terms root and stem are sometimes used interchangeably. However, there is a subtle difference between them: a root is a morpheme that expresses the basic meaning of a word and cannot be further divided into smaller morphemes. Yet a root does not necessarily constitute a fully understandable word in and of itself. Another morpheme may be required. For example, the form struct in English is a root because it cannot be divided into smaller meaningful parts, yet neither can it be used in discourse without a prefix or a suffix being added to it (construct, structural, destruction, etc.)  A stem may consist of just a root. However, it may also be analyzed into a root plus  derivational morphemes  . . .. Like a root, a stem may or may not be a fully understandable word. For example, in English, the forms  reduce  and  deduce  are stems because they act like any other regular verb--they can take the  past-tense  suffix. However, they are not roots, because they can be a nalyzed into two parts,  -duce, plus a  derivational  prefix  re-  or  de-.So some roots are stems, and some stems are roots. ., but roots and stems are not the same thing. There are roots that are not stems (-duce), and there are stems that are not roots (reduce). In fact, this rather subtle distinction is not extremely important conceptually, and some theories do away with it entirely.(Thomas Payne,  Exploring Language Structure: A Students Guide. Cambridge University Press, 2006) ​Irregular Plurals Once there was a song about a purple-people-eater, but it would be ungrammatical to sing about a purple-babies-eater. Since the licit irregular plurals and the illicit regular plurals have similar meanings, it must be the grammar of irregularity that makes the difference.The theory of word structure explains the effect easily. Irregular plurals, because they are quirky, have to be stored in the mental dictionary as roots or stems; they cannot be generated by a rule. Because of this storage, they can be fed into the compounding rule that joins an existing stem to another existing stem to yield a new stem. But regular plurals are not stems stored in the mental dictionary; they are complex words that are assembled on the fly by inflectional rules whenever they are needed. They are put together too late in the root-to-stem-to-word assembly process to be available to the compounding rule, whose inputs can only come out of the dictionary.(Steven Pinker, The Language Instinct: How the Mind Creates Language. William Morrow, 1994)