nicer
Nicer
nicer
nicer
nicest, nicer
more nicely
nicer, nicest
nicer, nicest
nicer, nicest
Yes, it is. It is the comparative form of the adjective nice (more nice).
No. The word nicer is a comparative form of the adjective nice. The adverb is nicely and the comparative would be "more nicely." (*The term "play nice" is just a colloquial form; play nicely is correct.)
The comparative form of new is newer (from 'moRE new')The superlative form of new is newest. (from 'moST new')
The comparitive form of the word nice is nicer, but whatever you do, don't just add 'er' onto the end of every word to make it comparitive!