Why are we getting introduced to both the Subjunctive and the Imperative at the same time, with only three lessons? Both of these topics seem like they need much more introduction/practice, and they need to be split into their own units. Did DL just get lazy near the end of the tree here or am I missing something?
They're related, both grammatically and thematically. In Spanish, they share the same grammatical structure; you tell them apart by whether or not there's something in the sentence that indicates wishfulness ("I hope...") or imagination ("If only...").
More to the point, the imperative is a special case of the subjunctive: when I tell you to do something, what I'm actually doing is hoping or expecting that you'll follow my command.
This is true in English as well: "Follow me" can be restated as, "If you would follow me," which is more formal (and quite obviously in the subjunctive) but otherwise means the exact same thing.
"You guys" is indeed the 2nd person plural.
Vosotros is the informal 2nd person plural used in Spain (duolingo teaches Latin American Spanish)
Ustedes is the formal 2nd person plural in Spain, and the only 2nd person plural in Latin America
So if you were talking to a group informally in Spain, you'd use the Vosotros form; if you were talking formally to a group in Spain you'd use the Ustedes form; & if you were talking to a group in Latin America you'd use the Ustedes form.
Both sentences are correct. And both of them are imperative. But there is a little problem with the second sentence.
The first sentence, "Llama (a) una ambulancia" is for the second person singular (tú). It uses the imperative form.
The second sentece, "Llamen (a) una ambulancia" is for the second person plural (ustedes). It uses the subjubtive form.
There is an explanation. "usted" and "ustedes" use the third person form of the verbal tenses (singular and plural respectively) but there is not third person form in the imperative so the subjuntive is used.
Example: "Call an ambulance"
Tú: "Llama ..." (Imperative)
Usted: "Llame ..." (Subjuntive)
Vosotros: "Llamad ..." (Imperative)
Ustedes: "Llamen ..." (Subjuntive)
PS- I want to use this comment for a second "lesson". In English you "call someone/something" The correct form in Spanish is "Llamar a alguien/algo" with the "a" preposition. Omitting the "a" is really normal in the daily use (specially in latin american Spanish which is strongly influencied by the USA and the english word "call") but is not correct.
The verb "llamar" (to call) appears always in the way of "llamar a algo/alguien" regardless if you are calling a person or a thing. There is an exception, when you use the verb without any object. Examples:
Llamo a mi madre = I call my mother
Llamas a una ambulancia = You call an ambulance
Me llamarán mañana = They will call me tomorrow ("me" means "a mí")
Llamó ayer = He called yesterday (There is no DO or IO, so we do not use "a" because you are not telling who are you calling)
The problem is that there are some part of Spanish speaking countries where people do not use the "a" because they are not used to say it that way.
My recommendation is to learn the verb "llamar a" instead of only "llamar" because is the correct form. Then if you go to somewhere where people do not use the "a" you can omit it.
Highly recommend the front section of 501 Spanish verbs by Kendris and Kendris. It has a really really helpful explanation of all the verb forms and examples. If only I had read it years ago. I just had been using the verb part, without the explanations. It really helps. I got the copy I am using at a garage sale or a thrift store. But definitely worth the full price.
In front of words that start with a vowel sound "an" is used in English. It makes it easier to say it out loud and sounds smoother. An equivalent example in Spanish is using "el" in front of feminine nouns that begin with a stressed "a" sound, for example, el agua, el hacha (hacha is the Spanish word for an axe. Note: "an axe", not "a axe"). Feminine words beginning with an unstressed "a" sound tend to have it blend in with the preceding "a" sound of la, for example, la hablante ("the speaker", a woman) sounds more like lablante when spoken. For words that have an initial stressed "a" sound you want to preserve the initial "a" sound, and so you end up with el agua instead of la agua which would, when spoken, tend to blend in to lagua. Many years ago in England it was common to drop a leading "h" when speaking and so "a hotel" was often spoken as "an 'otel". It is all about what sounds smoother and what flows off the tongue more naturally when speaking.
In the first two places (between checkpoints), there were some dificult things. Mainly in the second section. But after that it was pretty easy, just a lot of vocab stuff. I cannot believe there is only ONE lesson in the "haber" section! It is one of the most important helping verbs!
The sentence is an comand, so the imperative tense is used. The thing is that the imperative is made with the same endings as the present tense of the subjunctive except in the "tú" and "vosotros/as" forms, which have specific forms.
"llama a una ambulancia" uses the "tú" imperative, while "llamen a una ambulancia" uses the "ustedes" form. Both are imperative, no subjunctive. But the imperative for "ustedes" is the same as the subjunctive (llamen)