Pudo/podía

Question

I appreciate the inclusion of this lesson as an effort to educate us in a nuance. My particular American English formed brain just can’t seem to grasp the subtle differences. I’m wondering if in conversation with a native speaker, it would be an issue if the non-native speaker didn’t differentiate between the two forms. I think if I were speaking in Spanish and trying to explain a situation about not being able to open a door last night, I would choose words that made it clear that number one: He just couldn’t open the door or 2, at first, he couldn’t open the door, but then someone came to help him. Well, now that I’ve written out these examples, I realize how far I am from understanding the nuance. I’m hoping you will say that in conversation with a native speaker it really doesn’t make a lot of difference.  Verdad?

Silvia Píriz · Accepted Answer

Hola Julia M.
Great question! This distinction is certainly one of the trickier nuances in Spanish and the good news is that, in everyday conversation, native speakers will almost always understand what you mean from the context.
That said, there is a meaningful difference:

No podía abrir la puerta generally means he wasn't able to open the door (it describes the situation or inability, without telling us whether he eventually succeeded).
No pudo abrir la puerta means he couldn't open the door in the sense that there was a specific attempt and he failed. It refers to the outcome of that particular event.

So, in your second example ("At first he couldn't open the door, but then someone came to help him"), no podía abrir la puerta is the more natural choice because the inability was temporary and later changed.
If you accidentally use one instead of the other, native speakers will usually understand you perfectly well. Mastering this distinction will simply make your Spanish sound more precise and natural over time.
Hasta pronto
Silvia