threshold vs brink

threshold and brink both are nouns.

Word	Noun	Adjective	Verb	Adverb
threshold	Yes	No	No	No
brink	Yes	No	No	No

As nouns, threshold and brink are synonyms defined as:

Other synonyms of threshold include verge.

threshold (noun)	brink (noun)
the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway	the limit beyond which something happens or changes
the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close	the edge of a steep place
the smallest detectable sensation	a region marking a boundary
a region marking a boundary
the starting point for a new state or experience