How to Translate the Latin Legal Phrases Arguendo and Bona Fide into English

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Lawyers and the court system often use Latin phrase to describe circumstances, conditions, or situations pertinent to proceedings. By using universal Latin phrases it is less likely that these circumstances will be misunderstood. Throughout the Medieval and Renaissance periods, Latin was the language of science, theology, and diplomacy. Naturally, as modern law developed during these periods, Latin had an important impact on the legal system still felt by modern practitioners.

As the mother of the Romance languages, Latin bears little resemblance to English’s Germanic roots. Structure, grammar, and lexicon all differ greatly between these two languages, making Latin a difficult language to learn for native English speakers. Translating Latin phrases is a good exercise in learning Latin grammar as well as exploring the possible meanings of these phrases given only one or a few words per phrase. Arguendo and Bona Fide are two Latin phrases often used in law; their meanings describe two specific situations.


The word arguendo is commonly translated to mean “for the sake of argument” or “ for argument’s sake.” It is used in legal and academic settings to indicate when the speaker is about to make a point and is asking the listener to take an assumption for granted. For example, were a speaker to say:

“Arguendo, let’s say that Michael did indeed enter the dry cleaning store on the day in question. Does this make him guilty of robbery?”

The speaker in this case is asking the listener to entertain an unsubstantiated statement or assumption. Notice that the speaker’s question is dependent on the previous arguendo statement.

As with many Latin phrases used in English, the literal translation of arguendo has been lost in favor of a more convenient metaphoric meaning. The modern translation “for the sake of argument” is not technically correct.

The word arguendo is derived from the Latin word arguo (aguere, argui, argutum), a second conjugation verb meaning “to make clear,” “to declare,” or “to prove.” The –nd– portion of the word gives away that the verb is in its verbal noun or gerund form. Recall that English verbs can be turned into gerunds by adding –ing to the verb’s stem. For example:

like (verb), liking (gerund)

walk (verb), walking (gerund)

Putting a verb in its gerund form essentially turns a verb into a noun which may then, for example, function as the subject of a sentence.

Given the –o ending, arguendo may be either dative or ablative. In this particular case, the word is in the ablative and is a good example of the ablative of manner. This ablative construction is used to indicate in what manner something is done. Coupled with its gerund form, arguendo may be appropriately translated as “by arguing.” Were we interested in a literal translation into Latin for the phrase “for the purpose of argument,” an appropriate translation would be “gratia argumenti” which is not unlike ars gratia artis, “art for the purpose [sake] of art.”

Bona Fide

Bona fide is a Latin phrase found in everyday language. One may say, “that is a bona fide offer” to indicate that the offer is genuine. However, English speakers pronounce this phrase using English conventions, i.e. changing of the –i– from short to long by the addition of a silent –e in fide. In conventional Classical Latin pronunciation, Bona Fide should be pronounced as “bone-uh fee-day.” This phrase means the same in everyday language as it does in the legal profession. It is used to indicate something that is genuine, the real deal, or something for which nothing is at fault. However, the legal profession prefers the translation “in good faith” and is often used to indicate an assumption of benevolence on the part of a person, especially a person giving testimony.

The word bona is simply the feminine form of the word bonus –a –um, an adjective meaning good. On its own, this word may be in either the nominative or ablative case. We know it is feminine (rather than neuter plural) because it is an adjective modifying the feminine noun fide that can only be in the ablative case. Fide is a member of the uncommon fifth declension whose ablative singular case is similar to the third declension. As an noun, fide means “trust,” “confidence,” or “faith.”

This phrase is an example of the ablative of manner, a construction similar to the ablative of means. However, unlike the ablative of means, the ablative of manner indicates how something is done rather than with what. Therefore, in the ablative case, bona fide can be literally translated as “with [in] good confidence [trust].” This is one of the seemingly rare times when a Latin phrase has not lost its literal translation or meaning over centuries of use.

Things to Consider

Although conceptually similar, there are distinct differences between the ablative of means and ablative of manner. Both are phrases that indicate more information about how or with what something is done. Often, the ablative of manner is coupled with the preposition “cum” when no adjective is supplied. However, if the phrase or word is modified by an adjective as is the case with bona fide, the preposition is often dropped and must be artificially supplied by a translator.

The ablative of means never takes a preposition. This fact makes translation by Latin students difficult, because they often look for clues such as prepositions to properly translate Latin into English. The solution is to memorize the different ablative constructions and train oneself to look for the ablative case with absent, albeit expected, prepositions.