We don’t really have much of a subjunctive mood in English — it’s an entirely new set of conjugations in Spanish, but in English you essentially just phrase things differently. Indicative: “Although he’s attractive, I won’t sleep with him.” Subjunctive: “If he were attractive, I wouldn’t sleep with him.” In Spanish, you can say the same thing with only the tense changing. Indicative: “Aunque es atractivo, no dormiré con él.” Subjunctive: “Aunque sea atractivo, no dormiría con él.” Or something like that.

Anyway, I think the wiki article on the subject is super-fascinating. We don’t usually even have any idea what subjunctive is. This is the coolest part: “The verb ‘be’ is so distinguishable because its forms in Modern English derive from three different [emphasis mine] Old English verbs: beon (be, being, been), wesan (was, is), and waeron (am, art, are, were).” WHAT?

I started thinking about it when I was explaining how you had to say “If I were smarter” rather than (the seemingly correct, and oft-misused) “If I was smarter”. Of course, both sound okay — but the former is subjunctive (to be is only conjugated as “were” in subjunctive) while the latter, while carrying the same meaning, doesn’t really fit. (Both express an unreal situation, so both fall into subjunctive.) In Spanish, it should be “Si fuera más inteligente…” Unsure Spanish-speakers like me might say something else (“If I am smarter”?)… For example, even here I’m unsure: it could also be “Si sea más inteligente…”, although I think conditional statements don’t use present subjunctive. The real problem is that the use is a lot more complex in Spanish, so you can’t really understand it by translation.

(Edited a day later to be more understandable and correct a mistake.)