Here's why:
* -ing is added to the verb "understand" to create the noun "understanding."
* This "-ing" form acts as a derivational morpheme because it changes the word's part of speech (from verb to noun) and its meaning.
Let's break it down:
* Understand: Verb - to grasp the meaning of something.
* Understanding: Noun - the ability to grasp the meaning of something, or a comprehension of something.
While "-s" is also present in "understandings," it's an inflectional morpheme, indicating the plural form of the noun. It doesn't change the word's meaning or part of speech.