What term is used for a substance that has a pH of 8 or greater?

A substance that has a pH of 8 or greater is classified as a base. The pH scale ranges from 0 to 14, where values below 7 indicate acidity, a pH of 7 denotes neutrality, and values above 7 are considered basic or alkaline. Therefore, any substance with a pH of 8 or higher has more hydroxide ions (OH⁻) compared to hydrogen ions (H⁺), which is characteristic of bases.

When discussing other options, acids would have a pH less than 7, which does not apply here. Neutral substances, like pure water, have a pH of exactly 7. Salts are formed from the neutralization reaction between an acid and a base, and their pH can vary depending on the specific salts and their dissociation in water; they are not specifically categorized solely by a pH of 8 or greater. Thus, the correct and defining term for the given pH range is base.