2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/191924We point out the possibility of the {\em partial} conservation of the seniority quantum number when most eigenstates are mixed in seniority but some remain pure. This situation occurs in nuclei for the $g_{9/2}$ and $h_{9/2}$ shells where it is at the origin of the existence of seniority isomers in the ruthenium and palladium isotopes. It also occurs for $f$ bosons.Accepted for publication in Physical Review LettersNuclear Theorytext