1. Root

Root is morpheme on which the rest of a word is built. Root morphemes can be either free or bound. Free morphemes were traditionally called roots, and bound morphemes affixes.

Modern linguistics find that there are a number of components of words which appear like roots but cannot be used independently in speech or writing. For example, ceive in receive, perceive, conceive, deceive.

2. Base

Base is the part of a word to which an affix is attached. A base can be a root or more than one plain root. A base can also consist of a root plus one or more affixes.

3. Stem

Stem may be base to which a grammatical affix may be added. The stem of a word is the word form minus its inflectional affixes.

4. Relationship between them

Root, base and stem are related terms, but they are different from each other. Roots are bases that cannot be analyzed further into morphemes. All roots are potentially bases, but not vice versa. A stem is therefore is a special kind of base. All stem bases can be stems in English because some lexical categories don’t take grammatical affixes.