Inbreeding Coefficient
The Inbreeding Coefficient (IC) is a mathematical measurement of the closeness of the relationship between two dogs.

The IC is expressed as a percentage.

The higher the percentage is, the more closely related two animals are.

The lower the percentage is, the more distantly related two animals are.

An IC score of 25% would be equivalent to mating a brother with a sister.  In most cases that would be considered a bad cross.

An IC score of 12.5% would be equal to mating a grandfather to a grand-daughter.  That is sometimes done by knowledgeable dog breeders to
"fix" a good trait.  This close a breeding should be done by knowledgeable breeders only and then only rarely.

High or low scores are neither"bad" nor "good".  The IC is just one tool among many that a breeder can use to determine the suitability of a
particular cross.

(Linebred dogs might have high scores and still be very good dogs.

Outcrossed dogs might have very low scores and yet still not be good dogs.)