the route from A to B is not necessarily the same as the route from B to A

题目

the route from A to B is not necessarily the same as the route from B to A
is not necessarily the same as the route 这段东西看得懂意思,但是谁能帮我细细讲讲语法规则

答案

not necessarily 是短语,不一定
从A 到B的线路 不一定和从B到A的线路完全一样.