Negative of a Adjectives

About half of Japanese adjectives end with い (i).  To form the negative of these adjectives, the same way we change ‘new’ to ‘not new’ or ‘big’ to ‘not big’, replace the い with く (ku) and add ありません (arimasen). 

So あたらしい (atarashii; new) becomes あたらしく ありません (atarashiku arimasen).

Similarly, いそがしい isogashii (busy) becomes いそがしく ありません(isogashiku arimasen; not busy)

Using nai  is a less formal way to form the negative.

Another way to form the negative of an ‘i’ adjective is to add ない (nai) rather than ありません. Thus あたらしい  (atarashii) becomes あたらしく ない (atarashiku nai).  This second method is less formal than the first one, so as they always advise, if in doubt, use the the more formal method, especially when talking to strangers.