Threshold is a versatile word that can be used in different contexts. It refers to the point at which something begins, changes, or is achieved. There are several synonyms that can be used in place of threshold. For instance, "brink" refers to the edge or margin of something, such as the brink of disaster. "Cusp" is another synonym that denotes the point of change, such as being on the cusp of a breakthrough. "Limit" is a synonym that refers to the point beyond which something can no longer continue, such as reaching the limit of development. Lastly, "border" is another synonym that denotes the edge of something, such as crossing the border into another country.