It's spinning on the long axis around a 17-degree precession.

沿长轴有 17 度的旋进。

Well, a is the semi-major axis, or half the distance along the long axis of the ellipse.

a 是半长轴，或者说椭圆长轴的距离的一半。

A longitudinal fetal lie is ideal, where the long axis of the fetus, which is its spine, lies along the maternal long axis—the mom's spine.

纵产式是理想的，胎儿的长轴（脊柱）和母亲的长轴（脊柱）平行。

The baleen consists of a row, on each side of the upper jaw, of about 300 plates or laminae, which stand close together transversely to the longer axis of the mouth.

鲸须由位于上颌两侧的一排大约 300 个板或薄片组成， 它们横向于嘴的长轴紧密排列在一起。