降级数

Descending \De*scend"ing\, a.
Of or pertaining to descent; moving downwards.

{Descending constellations} or {Descending signs} (Astron.),
those through which the planets descent toward the south.


{Descending node} (Astron.), that point in a planet's orbit
where it intersects the ecliptic in passing southward.

{Descending series} (Math.), a series in which each term is
numerically smaller than the preceding one; also, a series
arranged according to descending powers of a quantity.