Putto best-known are the sculptor Donatello and the painter Raphael. The two relaxed and curious putti who appear at the foot of Raphael's Sistine Madonna are often reproduced. They also experienced a major revival in the 19th century, where they gamboled through paintings by French academic painters, from Gustave Doré’s illustrations for "Orlando Furioso" to advertisements. The iconography of putti is deliberately unfixed, so that it is difficult to tell the difference between putti, cupids, and various forms of angels. They have no unique, immediately identifiable attributes, so that putti may have many meanings and roles in the context of art.
Plural form of words ending in -us plural forms, also played a part. Nonetheless, the question of what the Latin plural of "virus" would have been in ancient times turns out not to be straightforward, as no plural form is attested in ancient Latin literature. Furthermore, its status as a neuter noun ending in "-us" and not of Greek origin obscures its morphology, making guesses about how it should have been declined difficult. The Latin word "vīrus" (the "ī" indicates a long "i") means "1. slimy liquid, slime; 2. poison, venom", denoting the venom of a snake. This Latin word is probably related to the Greek (')