"Who am I?"
Translation:Quis sum ego?
"Qui" is non-interrogative.
What book are you using? You may be getting the forms of the interrogative pronoun and the interrogative adjective (and by extension the relative pronoun) confused. They all have the same plural forms, only the singular forms differ (but many are the same or at least similar).
The feminine nominative singular interrogative pronoun is quis.
Quis sum? -> 'Who am I?' ('I' can be either male or female)
Quae would be the feminine nominative singular for the interrogative adjective and relative pronoun.
Quae femina sum? -> 'Which woman am I?'
Qui vir sum? -> 'Which man am I?' (For contrast with the masculine form of the adjective)
I am using a book called 'Lingua Latina per se Illustrata', which is written exclusively in Latin. Therein, one can read:
'Puer ridet. Puella plorat. Quis est puer qui ridet? Puer qui ridet est Marcus. Quae est puella quae plorat? Puella quae plorat est Iulia.
Marcus, qui puellam pulsat, puer improbus est. Puella quam Marcus pulsat est Iulia. Iulia Aemiliam vocat. Aemilia, quam Iulia vocat, mater liberorum est. Aemilia puerum verberat. Puer quem Aemilia verberat est Marcus.
Quem vocat Quintus? Quintus Iulium vocat. Iulius, quem Quintus vocat, pater liberorum est. Iulius Quintum non audit. Quem audit Iulius? Iulius Marcum audit. Puer quem Iulius audit est Marcus.
Puella quae cantat laeta est. Puella quae plorat non est laeta. Puer qui puellam pulsat improbus est!'
As a side-note, I am not entirely certain as to what mater liberorum and pater liberorum might mean. Unbiased mother/father? But then why the genitive case?
Maybe the use of quae here is something I am not familiar with. I can't seem to find any other source to corroborate this usage, but maybe someone can. In Wheelock's Latin, in A Primer of Ecclesiastical Latin by John F. Collins, and in Allen and Greenough's they do not show quae as being apart of the interrogative pronoun.
There are a few usages of words and such in Lingua Latina per se Illustrata that I am not overly familiar with due to mainly being from a Wheelock's background. I have LLPSI but have yet to have time to go through it. Someone else will have to give their input, would be curious about this usage.
Mater liberorum and pater liberorum mean 'the mother of the children' and 'the father of the children'. Līber (the adjective for 'free') can be used in the masculine plural as a noun to mean children.
Thank you for shedding light upon the meaning 'mater/pater loberorum'.
Moopish, just for the record, I am not learning Ecclesiastical Latin that is sprung from Vulgar Latin, the grammar and pronunciation of which, in my assessment, is simplified. No, I am learning Classical Latin.
So, what is the verdict?
After finding this discussion and reading through Allen and Greenough's entry on Relative, Interrogative and Indefinite Pronouns to verify; a suggestion that quis can be used as adjective could make sense of it.
The only sentences that you gave from LLPSI that threw me off a little were: Quis est puer qui ridet? and Quae est puella quae plorat? All other forms seemed to make sense as the interrogative adjective or the relative pronoun.
But if quis is sometimes used as an adjective then I could see quis then modifying puer in the first sentence to get something more literally translated as "Which is the boy who is laughing?" potentially more asking us to pick from the characters we have already been introduced to. And the same for quae modifying puella.
So the book makes sense in what it is doing, not sure about something like Quae sum (ego)? without an identifying noun, like feminia since that site suggests quae is an adjective. It only suggests that quae can be used substantively when it is being used as an indefinite adjective from what I read.
I could be wrong and welcome anyone's insight.
Many people have challenged DuoLingo's grammatical rules regarding 'quis' and 'quae', as can be seen.
This is why I definitely recommend more resources than just Duolingo. As much as I appreciate Duolingo, there is much that it still does not explore or expand on.
It seems we are both right, though if we are to focus on Classical Latin rather than Late Latin, you are closer to the truth, which is a surprise to me. This is a citation that I have found.
'If the gender is known to be feminine, both quis and quae can equally well be used as the question word, with the former preferred in earlier Latin and the latter in Late Latin.'
No worries, always looking for new sources myself as well to make sure I have the best understanding I can of Latin.
Wheelock's Latin, Oxford Pocket Dictionary, Allen and Greenough’s New Latin Grammar for Schools and Colleges (this one also mentions the ques form being in older Latin) on the Dickinson College Commentaries site are the main sources I use.
I tend to only quickly pop to Wiktionary and if I need more usage information I go to one of the sites that gets cited.
I have several other books as well but they tend not to get a look through as often when I need to look something up.