前后的英文：
an approximate time
from beginning to end
everywhere; all about

Backwards and forwards
前后;彻底地

A tandem bicycle
前后双座[连座]自行车,协力车

(also Christmas-time,Christmas-tide)period of several days before and after Christmas Day
圣诞节节期(圣诞节前后的几天)

Continuity is ensured by using the same props in successive scenes.
在连续的场景中使用同样的道具以确保前后衔接。

Articulated with the tip of the tongue turned back and up toward the roof of the mouth;retroflex.
卷舌音的舌尖在嘴中前后上下运动而发出清晰的声音;卷舌音的

A woman's ornate headdress, fashionable around1700.
女士装饰华丽的头饰，在1700年前后流行。

Ride tandem
两人(以上)前后纵排地乘坐(自行车)[(协力车)]

He sent out a few cautious feelers and received some contradictory answers.
他作过几次谨慎的试探，得到的答复前后不一。

To move (something) back and forth steadily or rhythmically.
摇动前后稳定而有节奏地移动（某物）。

Byzantine architecture
拜占庭式建筑((五至六世纪前后以拜占庭(Byzantium)为中心盛极一时的建筑式样))

first approximation
第一次近似;第一近似值;初步近似;一次近似值;一级近似;首次近似

a crude sketch, method, approximation
粗略的草图、 方法、 估计

It's derivation involved no approximation.
这种近似方法的适用性将在后面再讨论。

discrimination time
辨别时间辨别时间

It is time to go.
该走了。

They are not in step with the times.
他们跟不上时代的步伐。

It is beginning to dew.
在结露水了。

The scrambling begins.
混乱开始了。

The days are beginning to shorten.
白天开始变短了。