Thionic acid, also known as sulfuric acid or sulfonic acid, is a powerful chemical compound used in various industrial applications. Synonyms for thionic acid include hyposulfurous acid, dithionic acid, sulfurous acid, and sulfonous acid. These alternative names stem from the compound's composition and properties. Thionic acid, or its synonyms, is commonly employed in the production of dyes, pharmaceuticals, and as a reducing agent in various chemical processes. It is essential to note that while these names are often used interchangeably, each synonym represents a slight variation in chemical structure or specific application.