Ciro Santilli @cirosantilli 40

A gene that got duplicated withing the same species. The copies may diverge in function from the original.

Important example: hox genes.

Kind of a synonym for hydrogen emission spectrum not very clear if fine structure is considered by this term or not.

A line set for hydrogen spectral line.

Formula discovered in 1885, was it the first set to have an empirical formula?

Approximation to Huygens-Fresnel principle.

Like the special orthogonal group is to the orthogonal group, $SO(m,n)$ is the subset of $O(m,n)$ with determinant equal to exactly 1.

The fact that this foundation has a bunch of paid, closed, certification courses makes Ciro Santilli not respect them at all. They should be making open access content instead!