* Making something more of something: In "broaden" and "widen," it means making something wider or broader.
* Becoming something: In "strengthen," it means becoming stronger.
* Performing an action: In "harden," it means to make something hard.
Essentially, "-en" is a verb-forming suffix, turning adjectives or nouns into verbs that describe an action of making something more of what the base word describes.
Here are some other examples:
* Deepen: To make something deeper.
* Lengthen: To make something longer.
* Strengthen: To make something stronger.
* Soften: To make something softer.
* Sweeten: To make something sweeter.
It's important to note that not all words ending in "-en" follow this exact pattern. Some words have different origins or meanings, like "golden" or "wooden." However, in the context of words like "broaden" and "widen," "-en" clearly indicates a change in state or condition.