If I want to ask the question about the dog, whose name is
Cerberus should I ask
Quis est Cerberus?
Quid est Cerberus?
Do we use
quae (according to gender) about animals or
What is the rule here?
Latin Language Stack Exchange is a question and answer site for linguists, teachers, and students wanting to discuss the finer points of the Latin language. It only takes a minute to sign up.Sign up to join this community
I've had a hard time finding examples of a sentence of this form from a Latin corpus. However, my guess would be that when quid is used as a substantive/pronoun with the sense of what, it does not change its form according to the gender of other nouns in the sentence. The same for quis used as a pronoun in the sense of who. (Although depending on the era, I think quae might be used as an interrogative pronoun if you know somehow that the answer to the question will be a woman. See Brutal Russian's answer here: Confused about the use of “quae” as an interrogative word)
So I think it would be "Quis est Cerberus?" if you mean to ask "Who is Cerberus"/"Cerberus is who?", and "Quid est Cerberus?" if you mean to ask "What is Cerberus?"/"Cerberus is what?"
And in the unlikely event that you meant to ask something like "Which [of these women] is Cerberus?", it could even be "Quae est Cerberus?"
Compare English: "What is Cerberus" and "Who is Cerberus" are both valid sentences; they just mean different things.
Of course, Latin is not English. But similarly, compare the use in Latin of id vs. is: I believe id est Cerberus and is est Cerberus are both grammatically valid. Since a demonstrative pronoun like is/id does not have to agree with the gender of the other noun in copular construction, I don't think the interrogative pronoun quis/quid has to agree in this construction either.
I was only able to find some reddit posts about this topic, nothing very detailed or authoritative:
Also the questions listed in this handout "Developing oral skills in Latin", from the website of the New York State Education Department, show usage of quid vs. quis according to the meaning of the pronoun, not in agreement with the other noun in the sentence:
Ask the following questions
Teacher: Quid est Campus Martius?
Student: est locus
Teacher: Nunc quid est Spartacus?
So there is evidence at least that this is a pattern used by modern speakers of Latin as a second language who have English as their native language.