答案:A root is the base form of a word that cannot further be analyzed without total loss of identity. That is to say, it is that part of the word left when all the affixes are removed. In the word internationalism, after the removal of inter-, -al and -ism, what is left is the root nation. All words contain a root morpheme. A root may be free or bound. E.g. black in blackbird, blackboard and blacksmith; -ceive in receive, conceive and perceive. A few English roots may have both free and bound variants. E.g. the word sleep is a free root morpheme, whereas slep- in the past tense form slept cannot exist by itself, and therefore bound.A stem is any morpheme or combination of morphemes to which an inflectional affix can be added. E.g. friend- in friends and friendship- in friendships are both stems. The former shows that a stem can be equivalent to a root, whereas the latter shows that a stem may contain a root and a derivational affix.