Nonacid is a term used to describe substances that are not acidic in nature. Some common synonyms for nonacid include alkaline, basic, neutral, and non-alkaline. Alkaline refers to substances that have a pH higher than 7, which is neutral. Basic is another word for alkaline and means the same thing. Neutral is used to describe substances with a pH of 7, which means they are neither acidic nor alkaline. Non-alkaline refers to substances that are not alkaline in nature. These synonyms are useful when discussing the chemical properties of substances and their interactions with other substances.