  The Gell-Mann$-$Okubo (GMO) mass relations following from
$\text{SU}(3)$-flavor symmetry breaking in the strong sector have been proven
to be of great success for describing hadron masses and classifying them into
multiplets. Nowadays, it is widely believed that baryons being fermions have to
obey GMO relations which are linear in the baryon masses, whilst mesons as
bosons follow quadratic GMO relations. In this work, I challenge the
distinction of GMO relations for baryons and mesons and conclude that both
linear and quadratic GMO relations apply to both baryons and mesons in most
instances (exceptions are the pseudoscalar meson octet and the mass relations
following from heavy quark symmetry). I support this claim by presenting an
in-depth analysis of the GMO relations on a theoretical and experimental level.
On the theoretical side, two approaches to the derivation of the GMO relations
are given and isospin symmetry breaking, electromagnetic contributions, and
heavy quark symmetry are incorporated into the mass relations. Both linear and
quadratic mass relations are checked against experimentally determined hadron
masses. Furthermore, the mass relations are used to classify unassigned
resonances like $\Lambda^+_c(2940)$ and $\Xi_c(3123)$ into multiplets and to
predict the masses of missing particles in yet incomplete multiplets.
