* Simple and direct: The constant criticism from her boss undermined her confidence.
* With an object: The scandal undermined the politician's credibility.
* In a metaphorical sense: The lack of funding undermined the project's progress.
* With an adverb: The constant changes in policy seriously undermined the team's morale.
* In a passive voice: Her authority was undermined by her colleagues' gossip.
Remember that "undermine" implies weakening or damaging something from the foundation up, like digging away at the base of a building.