What is the difference between repentance (tawbah) and sincere repentance (tawbah nasūḥ), and does repeating a sin after repenting invalidate it?

Repentance in general is that which fulfills its conditions. As for sincere repentance (Al-Tawbah Al-Nasuh), the expressions of scholars and people of spiritual insight have differed regarding it. Some said: It is that from which there is no return to the sin thereafter. Others said: It is to detest the sin that one once loved. And some said: It is that for which one does not feel secure about its acceptance and remains in awe of it. It was also said: It is regret in the heart, seeking forgiveness with the tongue, abandoning the sin, and feeling reassured that one will not return to it. And some said: It is the restitution of injustices, seeking pardon from adversaries, and persisting in acts of obedience.