It is common in western culture to depict the fruit of the tree of the knowledge of good and evil as an apple. However, a brief flip through Genesis will confirm that the forbidden fruit remains anonymous; there is no mention of an apple nor any other fruit. The universal use of the apple results from a minor mistranslation of the Vulgate, the Latin version of the Bible. Allow me to explain.
The first rule I was taught in Latin was that adjectives always agree in case, gender, and number with the nouns they modify.1 This basically means that the ending of an adjective will always match that of the noun it is describing.2 For example, a bonus servus is a “good servant,” a bona femina is a “good woman,” and a bonum donum is a “good gift.” In a glossary, Latin adjectives are often written with both the root word and the endings, like this: bonus -a -um.
Now that you understand that, let us return to the case of the apple. I spoke of the Latin Vulgate and how the misunderstanding originated from that text. It is really very simple. The Latin word for apple is “malum.” The Latin adjective for evil is “malus -a -um.” So, friends, an evil apple is a “malum malum.” When our oh-so-intelligent medieval ancestors read the Vulgate, one of them misinterpreted malum “evil” to mean malum “apple,”3 and thus inspired the universal idea that the forbidden fruit was an apple.
1Latin nouns are sorted into categories and “cases” are one of these categories. There are five cases in Latin and these determine the noun’s grammatical role in a sentence (e.g. whether the noun is the subject, object, indirect object, etc.). Latin nouns also have “genders.” These genders have nothing to do with the actual gender of an object, except when dealing directly with people. For example, a servus is a male servant and a serva is a female servant. “Number” refers to whether the noun is singular or plural.
2I say always, but this is not strictly true. An adjective will always match its noun in case, gender, and number, but this does not necessarily mean that the ending will look the same.
3I have heard it rumoured that St. Jerome, who translated the Bible into Latin, purposely translated fruit as malum “apple,” but I do not know if this is true.