Talk:The Sacrifice/@comment-2600:1:B25D:A6A0:9AF:BFD0:2638:9917-20180502190403/@comment-63.140.74.243-20180508005745

Or it could mean, as it is stated on the wiki, "Lambda indicates the wavelength of any wave, especially in physics, electronics engineering, and mathematics.". Basically third wave, or third wave of warframes, aka Umbra.