"I have an appointment with the doctor."
Translation:Tengo una cita con el doctor.
I think so. Usually nouns that end with an 'a' are feminine, and ones that end with an 'o' are masculine. Doctors can be male or female, and the grammar sounds okay, so I think it should be fine. Sometimes Duo needs a more literal translation though, so if it is 'doctor' instead of 'doctora' it is probably best to stay with the masc.
You may think as in English, because it's basically the same.
When expressing professions: I am a postman, I am a doctor, I am..., in English you use "a". This would be equivalent to say in Spanish: Soy un cartero, soy un doctor, soy .... and it would be somewhat valid. This meaning that you may encounter this, though it's rare.
The normal approach is just to drop the article: Soy cartero or trabajo de cartero.
When referring to a specific postman, it's obvious that you need an article. So, for instance, if I meet a chap dressed in yellow, yellow bike, a large bag full of envelopes (you get where I am going) at the entrance of my block and ask: who are you? He will say: I am the postman; Yo soy el cartero.
The so-called ‘personal a’ is used for animate determinate direct objects. In this sentence, ‘la doctora | el doctor | la médica | el médico’ is animate and definite, but is the object of the preposition ‘con’, not the direct object of the verb ‘tengo’. The direct object here is ‘una cita’, which is neither animate nor determinate.
Both the English “I have an appointment with the doctor.” and the Spanish ‘Tengo una cita con el doctor.’ refer to a particular doctor, presumably the doctor who has been the topic of an ongoing conversation, is the doctor in whose office the speaker is standing or whose office the speaker is calling, or is otherwise obvious from the context.
Duo doesn’t. I’d say, 60/40, Duo assumes the feminine.
Whether this is what the Spanish do, I don’t know. I get the feeling, though, that masculine is usually assumed, especially for plural, since unlike English or German, Spanish does not lose gender in the plural.
Which is where Duo often confuses me the most: When they use “ellas,” that does seem to specify female plural, as in women or girls, but the translation is always just “they.”
It would be nice if a native speaker chimed in on this one.