The stem or most basic part of a word that retains meaning is called:

a. Affix

c. Suffix

b. Prefix

d. Root

The stem or most basic part of a word that retains meaning is called D) root.

Affixes, which include suffixes and prefixes, are added to the root to achieve another meaning.

For example:

Happy - root; un (prefix) + happy (root) = unhappy - a new word