Immediately after the four relations, the source introduces another use of “particular”:
فصل: وقد يقال للجزئي معنى آخر، وهو ما كان أخص تحت الأعم؛
Section: “particular” may also be used in another sense, namely what is more specific under a more general concept.
This is relative particularity (juzʾī iḍāfī). “Human” remains a universal because it applies to many humans, yet it is narrower than “animal,” and thus a relative particular under animal.
The word relative signals that particularity is determined by comparison with a wider concept, not solely by how many individuals the concept can apply to.