Việt
mật chia
mặt lăn
Anh
primary surface
direct surface
Đức
Grundflaeche
Primaerheizflaeche
Pháp
surface directe
surface primaire
direct surface,primary surface /SCIENCE,ENG-MECHANICAL/
[DE] Grundflaeche; Primaerheizflaeche
[EN] direct surface; primary surface
[FR] surface directe; surface primaire
mật chia (bánh răng), mặt lăn