n fold extension 重扩张

n-fold axis 重轴

n-fold symmetry axis 重对称轴

n-fold pole n 阶极点

n-fold shooting 次激发 ; n次激发

accordion n fold 折页 ; 手风琴状褶皱

n-fold symmetry axis n 重对称轴

fan n fold 扇状褶皱

n-fold helix n次螺旋