You can use tier with a number to show how many rows or layers something has.
a three-tier wedding cake.
一个3层的结婚蛋糕。
You can use tier with a number to show how many levels there are in an organization or system.
the possibility of a two-tier system of universities.
大学实行双重体制的可能性。
tiers
A tier is a row or layer of something that has other layers above or below it.
the auditorium with the tiers of seats around and above it.
四周和上方有一排排座位的礼堂。
A tier is a level in an organization or system.
Islanders have campaigned for the abolition of one of the three tiers of municipal power on the island.
岛民们已经发起了运动,要废除该岛三级市政管理层中的一级。