"Sometimes my friend and I study on Tuesdays."
Translation:A veces mi amigo y yo estudiamos los martes.
It's simply a difference between the two languages. While in English we say "on" a particular day, in Spanish a definite article is used instead. When translating from Spanish to English, then, we turn the article into "on" to make the sentence make sense. I imagine Spanish-speaking English learners experience the same difficulty: "Why is there no 'the'? Where is this 'on' coming from?"
For practical purposes, we can consider that under most circumstances a definite article preceding the name of a day of the week can be translated to "on." "I go on Sunday." "Voy el domingo."
The exception to the need for an article involves many instances following the verb "ser." "Today is Sunday." "Hoy es domingo." This exception does not hold up, however, where the English sentence would say "is on" rather than simply "is." "The concert is on Sunday." "El concierto es el domingo."
When I hover over "study" the pop-up shows...(nosotros) estudiamos. Since I didn't see nosotros anywhere I estudian which was marked wrong, I'm guessing since the sentence mentions a "friend and I" that I should have realized that "friend and I" become "we" becoming an invisible "nosotros."
Amiga worked for me. Perhaps the error was elsewhere in your sentence. If you post your whole answer we can help figure it out. It can be confusing because Duolingo doesn't always tell you where your mistake lies, and it doesn't give all the possible correct iterations. So when you see that the 'correct' sentence Duo gives has "amigo" and you had put "amiga", it's be tempting to think that this is why you were dinged. It's possible that amiga wasn't accepted in the past and was updated before I answered the question. Hard to say unless we see your whole answer :)
It is not required to put nosotros, ustedes/ellos/ellas. I believe it is a preference unless you want to specify a gender. It also depends on the region.
(Yo) Estudio = I study (Tú) Estudias = You (informal) study (Él/Ella/Usted) Estudia = He/She/You (formal study (Ustedes/Ellos/Ellas) Estudian = you all (plural) study/ they (male) study/ they (female) study (Nosotros/Vosotros) Estudiamos = we study.
Estudian is multiple people studying, but not including yourself. Estudiamos is multiple people studying including yourself
The word "a veces" can go at the beginning (a veces my amigo y yo estudiamos los martes") to mean "sometimes, my friend and I study on Tuesdays (direct translation)". However, it can also go in the middle of the sentence, and be written as: "mi amigo y yo a veces estudiamos los martes," meaning "my friend and I sometimes study on Tuesdays"
I could be wrong, but I'm pretty sure the reason is that no action is being performed where the friend is a recipient of that action. An example of a sentence where you would use the personal "a" would be "Ayuda a tus amigos" (help your friends) or "Anoche, llamé a mi amigo" (Last night, I called my friend)
The plural of the day, "
los martes", is used because it is every Tuesday ("todos los martes"), hence "on Tuesdays", also plural, in the English version.
Using the singular, "
el martes" would mean on one specific Tuesday (eg "next Tuesday", "last Tuesday"), which would not make sense here with "sometimes" ("a veces").
El artículo definido en singular delante del nombre de un día de la semana indica un día determinado, concreto, mientras que el artículo definido en plural indica periodicidad: elblogdegramatica (blogspot.com)
Si algo ocurre siempre el mismo día de la semana, usamos el artículo definido y el día en plural y sin preposición: espanolplus.com
Christa75.., are you doing your lessons on a computer, or a smart phone app? If the program has a block of text appear on a device with a touchscreen that covers your sentence, you can touch it & drag it elsewhere on the screen to see your answer.
On a computer, it may be a problem of a page being sized wrongly for the screen, and you can try scrolling to see it, or changing a size setting that may have an option to show laptop or tablet text at 150%, or some other little aggravation that can be reset to your liking. Hope that helps.
I'm editing this because the smart phones no longer allow you to slide the "correction" off of your answer. It completely covers it, & I have reported it multiple times with the flag option, but do not know how to report it to the developers or programmers. This has been going on for at least five months.
Brian75..., moderators at Duolingo don't usually read things posted here; you need to hit the "report" icon or flag, on the previous page, where your answer was counted wrong.
But if you want to talk about it with people here on the forum, you need to cut & paste your answer or retype it exactly so they can help analyze where you may have made a mistake - your answer does not show up except to you, otherwise.
Occasionally, Dúo does have errors, especially when they are making changes in their program. I think they do a very good job on the computer translating, for their small staff and millions of followers!
You seem to be incorrect. You don't study Tuesdays. If you haven't ever typed Spanish before, words can vary in meaning with other words. If it is included between the 2 words, the definition is "on". "We study Tuesday." "We study on Tuesday." One is correct, one is incorrect. Hope this helps!