Emphasis on clarity:
* Clearly
* Obviously
* Plainly
* Explicitly
* Unmistakably
* Definitely
Emphasis on difference:
* Separately
* Individually
* Uniquely
* Differently
* Particularly
Emphasis on memorability:
* Vividly
* Sharply
* Strikingly
* Memorably
* Impressively
More formal synonyms:
* Notably
* Remarkably
* Significantly
* Specifically
* Emphatically
The best alternative will depend on the context of your sentence. For example, "He distinctly remembers the day" could be replaced with "He vividly remembers the day" or "He clearly remembers the day".