I'm new to the words heritability, liability and familial risk in GWAS studies and I have three questions.
Firstly, I know the definition of heritability is the percentage of variation of phenotype captured by variation of genotype (correct me if I'm wrong). However, what's a liability here? I see some writing like "heritability on the liability threshold scale spanned a wide range" and do not understand.
Secondly, I'm reading some cancer GWAS papers and often at the end author would make a statement like "new discovered loci captured XX% of familial relative risk". Why don't they use heritability rather than the percentage of familial relative risk?
Finally, if the heritability of one phenotype is "a%" and on average "b%" of familial relative risk can be explained by a set of loci, does it mean I can do simple math that "a%-b%" of phenotype variation can be explained by the rest of genome, or something else?