@some kR verbbases

kR कृ + /u + /laT
→ kar कर् + /u + /laT by sArvadhAtuk...
→ !**karu- करुॱ this base only appears before /pit endings, before the others we get **kuru- कुरुॱ

Before /pit endings, **karu- करुॱ becomes **karo- करोॱ normally, by gbH —

**karu- करुॱ + /laT /tip → !**karo- करोॱ + /laT /tip

So we say —

**karo- करोॱ + /tip → !**karoti करोति "makes"

**karo- करोॱ + /sip → !**karoSi करोषि "you' make", with /Satvam

**karo- करोॱ + /mip → !**karomi करोमि "I make"

But before non-/pit endings, **karu- करुॱ becomes **kuru- कुरुॱ by ata::utsArv....

**karu- करुॱ + /laT /tas → **kuru- कुरुॱ + /tas → **kurutas कुरुतस्

**karu- करुॱ + /laT /jhi → **kuru- कुरुॱ + /anti''' → **kurvanti कुर्वन्ति

**karu- करुॱ + /loT /sip → **kuru कुरु

kurute कुरुते

kurvate कुर्वते

**karu- करुॱ + /zatR m + /su → **kuru- कुरुॱ + /zatR m + /su → !**kurvan कुर्वन् "that is doing"