In this lesson we met two new terms: hinge and threshold.
Hinge is actually a piece that connects two fixed objects and allows them to move.
threshold is a piece of stone or wood that is passed when entering a building or room.
However we do not use them in this sense but in metaphorical meanings. hinge; a bond that holds two elements together while preserving their individuality, threshold; the point where two elements come together while they are independent of each other and serves as both a connection and a division.