/sup' / सुप्ऽ

"sup" is the plural /sup ending in the seventh line, /Gyossup.

It means in, at, on, about, and sometimes among —

**sat- सत् + /sup' → !**satsu सत्सु "among good people"

**vRkSa- वृक्षॱ + /sup'
→ vRkSe वृक्षे + su सु by bahuvacan...
→ vRkSe वृक्षे + Su षु with /Satvam
→ !**vRkSeSu वृक्षेषु "in trees"

**azva- अश्वॱ + /sup'
→ azve अश्वे + su सु by bahuvacan...
→ azve अश्वे + Su षु with /Satvam
→ !**azveSu अश्वेषु "about horses"

**suhRd- सुहृद् + /sup' → **suhRtsu सुहृत्सु "about friends"

**vidyut- विद्युत् + /sup' → !**vidyutsu विद्युत्सु "about lightning flashes"

IMPORTANT — the word su सु in sUtras means the first singular /su, not this /sup' here.

There is also a /sup term meaning "any ending in list svaujasamauTch...", so be careful —

The /sup' in rossupi means "the seventh plural ending /sup'"
The /sup in rosupi means "any /sup ending"