A word is an autonomous unit of language in which a particular meaning is associated with a particular sound complex and which is capable of a particular grammatical employment and able to form a sentence by itself.

A morpheme is also an association of a given meaning with a given sound pattern. But unlike a word it is not autonomous. Morphemes occur in speech only as constituent parts of words, not independently, although a word may consist of a single morpheme. Nor are they divisible into smaller meaningful units. That is why the morpheme may be defined as the minimum meaningful language unit.

Morphemes are subdivided into roots and affixes. The affixes are subdivided, according to their position, into prefixes, suffixes and infixes, and according to their function and meaning, into derivational and functional affixes, the latter also called endings or outer formatives.

For the word h e a r t y and for the paradigm

 h e a r t - h e a r t s the stem may be represented as h e a r t -. This stem is a single morpheme, it contains nothing but the root so it is a simple stem. It is also a free stem because it is homonymous to the word h e a r t.

To be continued.