Learn Arabic (Modern Standard): رجع الممرض من المستشفى.

The preposition من usually ends with a silent consonant sound. However, the next word المستشفى starts with "al-", which also begins with a silent sound when connected in speech. Arabic doesn't like having two silent consonants in a row, so the "n" in من gets a short "a" sound to bridge the gap. You pronounce the phrase together as "mina l-mustashfaa".

Is من always written as a separate word?

Yes! Unlike the attached prepositions you might have seen earlier (like ب for "with" or ل for "to/for"), من is a "separate preposition." It always stands alone as its own word and never physically attaches to the noun that follows it.

Why does the sentence start with the verb رجع (returned) instead of the nurse?

In Arabic, the most common sentence structure is Verb-Subject-Object. So, you literally say "Returned the nurse from the hospital." You could put the nurse first, but starting with the verb is the classic, standard way to build a sentence in Modern Standard Arabic.

What is the dotless letter at the end of المستشفى?

That letter is called an "alif maqSura" (broken alif). Even though it looks exactly like the letter ي without dots, it is actually pronounced as a long "aa" sound. It keeps this shape and sound even when it comes right after a preposition.

If the nurse were female, how would this sentence change?