What part of word carries the burden its meaning?

The part of a word that carries the burden of its meaning is the root or base word.

Here's why:

* Root: The core of a word, the part that conveys the fundamental meaning. For example, "act" in "action", "write" in "rewrite".

* Base word: The simplest form of a word, from which other words can be created by adding prefixes, suffixes, or changing the ending. For example, "play" is the base word for "playground", "player", and "played".

While prefixes and suffixes can modify or add to the meaning of a word, the root or base word is the foundation upon which the complete meaning rests.