Lag

A Lag is a non-magical creature who is born to at least one magical parent. Lags are, in essence, a magical-born human. They are rare and are looked upon with a degree of disdain by some members of the magical community, particularly purebloods.

Human-born magical creatures are descended from Lags who married humans; magical abilities and powers unexpectedly resurface after many generations and can often cause the human parents confusion.

Etymology
The term Lag comes from the Norwegian dialect lagga which means "slowly". It is generally used to mean that someone is "falling behind in movement, progress, or development".

The term was also intended to mean that this person was a break or period of rest in a bloodline.

Differences Between Lags and Humans
In addition to being born into magical rather than Human parents, Lags are different from humans by their knowledge of the magical community. they are able to see and take part in things that has been kept secret from the human world.

Lags are also contrasted with human relatives of magical creatures. Human parents, siblings, spouses etc. are simply humans who happen to know about the magical community through their blood relation.