يَدْعُو → لَمْ يَدْعُ → اُدْعُ
The first is the indicative imperfect. With لَمْ, the jussive drops the final weak consonant. A direct command is then formed by removing the imperfect prefix and adding connecting hamzah.
CategoryFormMain reason
Active perfectدَعَاWāw → alif
Passive perfectدُعِيَWāw → yāʾ
Active imperfectيَدْعُوFinal wāw retained
Jussive imperfectلَمْ يَدْعُWeak-letter deletion
Second-person commandاُدْعُJussive + connecting hamzah
Active participleدَاعٍWeak final yāʾ rule
Passive participleمَدْعُوٌّAssimilation of wāws
All seven forms remain linked to the root د ع و. The changing surface forms reflect separate rules, not separate roots.