Definitions for "Grade Separation"
A crossing between two transportation rights-of-way that is separated vertically. A transit right-of-way may be fully grade-separated or partially grade-separated.
The separation of pedestrians from other road users by a different in vertical level, typically an overbridge or an underpass/subway.
An intersection that is no longer at-grade (roads cross at the same level) because one road passes over the other on a bridge. Adding ramps to a grade separation, providing access from one road to another, creates an interchange.