Here's why:
* Root: The basic form of a word, carrying its core meaning (e.g., "play" in "playful").
* Prefix: A word part added *before* the root to modify its meaning (e.g., "un-" in "unhappy").
* Suffix: A word part added *after* the root to modify its meaning or grammatical function (e.g., "-ing" in "playing").
Endings are essentially suffixes that mark grammatical function. They often indicate things like:
* Plural: -s (cats)
* Tense: -ed (played)
* Possessive: - 's (cat's)
Example:
* Root: "play"
* Suffix (ending): "-ing"
* Word: "playing"
Therefore, endings are not added to prefixes or suffixes, but rather to the root of a word.