Something that is new has not been used or owned by anyone.
崭新的 • That afternoon she went out and bought a new dress. 那天下午她出去买了一条新裙子。
New is used to describe something that has only recently been discovered or noticed.
新发现的• The new planet is about ten times the size of the earth. 这个新发现的行星大约是地球大小的10倍。
This idea isn't new.
这主意不新鲜。
My new shoes squeak.
我的新皮鞋走路嘎吱嘎吱响。