1. in a basic or essential way; at the most important level
2. in a way that relates to the foundation or basis of something

Examples

• The two approaches are fundamentally different.
• She fundamentally disagrees with the new policy.
• The problem is fundamentally about communication.
• Their beliefs are fundamentally opposed to ours.
• The system needs to be fundamentally changed.
• He is fundamentally a good person.
• The theory is fundamentally flawed.