* Thinning: The nail polish remover, which is a solvent, thins the nail polish. The more remover you add, the thinner the mixture becomes.
* Altered Consistency: The consistency of the mixture changes. It can go from thick and viscous to a more watery, runny liquid.
* Color Change (potentially): If you add a lot of remover, it can slightly dilute the color of the nail polish.
* Reversibility (to a degree): While you've technically "reverted" the polish back to a liquid, it's not exactly the same as it was when it was first manufactured. The solvents in the remover have altered its composition.
* Potential for Use (with caution): If your nail polish has become thick and gloopy, adding a few drops of nail polish remover can thin it out and make it usable again. However, using too much can make the polish too thin and lead to poor coverage and longer drying times. There are products called "nail polish thinner" that are specifically designed to thin nail polish and avoid the negative effects of using nail polish remover.
In short: Nail polish remover dissolves nail polish, thinning it and changing its consistency. A little bit can help revive thick polish, but too much can ruin it.