thresholds
thresh-olds
noun
The bottom parts of doorways, forming the entrance to a room or building.
"The old house had worn wooden thresholds."
noun
Points or levels where something begins, changes, or becomes effective.
"Many countries are reaching critical climate thresholds."
Thesaurus
Synonyms: limen, doorway, room access, door, brink, verge, doorstep, doorsill