What's the difference between a "root" and a "stem" of a word? Why should one be the proper one that passes down and not the other?
A
stem is that part of a word to which inflectional suffixes are attached and which carries a fairly clear meaning. When forming compounds based upon a word, the stem should be used.
A
root is that part of a word that cannot be further reduced without losing the
core of the meaning. That core may be vaguer than the meaning of the stem, though some words have stems that are roots (and are called “root-stem word”).
When a stem is more than a root, the stem carries more semantic content. For example, the stem “justif-” carries more meaning than the root “jus-”, which is also found in “jussive”.
In addition to roots and stems are
bases. The distinction is that stems may have prefixes, whereas bases do not.
The stem of “unpackages” is “unpackag-”; the base is “package”; the root is “pack”.