noun
cusp
KUSP/kʌsp/
A point of transition between two states or periods.
The clocks show the cusp between one year and the next.

Etymology
A physical point or pointed end broadened into a figurative point where one state changes to another.
More examples
- The company stands on the cusp of a breakthrough.
- She is on the cusp of adulthood.
Forms
cusp
Similar words
- threshold
- Emphasizes the beginning of a new state.
- turning point
- Suggests a consequential change in direction.