In which cases should I use the subjunctive mood?
I suggest that every applicant fill out the form carefully.
If she were rich, she would live on Long Island.
What is called the "subjunctive" or the "present subjunctive" is in fact just a simple untensed variant of normally tensed that-complement clauses.
Unlike real subjunctive systems in languages like German or Spanish, this construction appears
Complement clauses are governed by their predicates. Which predicate you use controls what kind(s) of complement can be used with it, or whether it can have a complement at all. With impositive predicates (see lists below), that-complements must have a subject noun phrase (i.e, the subject NP can't be deleted), but in these that-clauses the verb form is infinitive, not present or past; i.e, the verb does not agree with its subject NP.
Since this construction is governed by the predicates it can occur with, and the predicates are all impositive -- i.e, they are predicates indicating that the speaker is imposing their will on the addressee -- the construction is associated with that concept, and traditionally "subjunctive" verbs were sposta "express" this "mandative" notion. Actually, of course, that's expressed by the predicate, and only emphasized by the use of this construction with it.
There are four patterns, with four different kinds of complement-taking impositive predicates:
There are other predicates, but if one learns these lists, one comes to recognize the semantic characteristics of impositive predicates, and thus to decide whether to use this construction with them, or others, or not. That's it for the "present subjunctive".
The "past subjunctive" -- which I will not deal with here -- is a different set of constructions altogether, completely distinct from the "present subjunctive" constructions, expressing nothing like their sense, and behaving in completely different ways.
The reason why they're both called "subjunctive" is because Latin had a subjunctive mood that was used in many ways, and these constructions reminded classically-educated grammarians of certain uses of the Latin subjunctive mood.
But in English they're just a couple more mildly idiomatic constructions, out of thousands. That's why obsessing about the English "subjunctive mood" is a waste of time and effort, and always ends up in confusion.
In general, the subjunctive mood should be used in "a statement contrary to fact, a wish, a mandative statement" (from this guide). I think "statement contrary to fact" could also often be considered a hypothetical, so I will refer to it as that.
In your first example, you are expressing a wish or possibly a mandative statement, "I suggest" and so it follows with a subjunctive: "every applicant fill".
In your second example, you have constructed a hypothetical, thus you use the subjunctive mood ("she were"). When you see "if" or "whether" used in a hypothetical way, it is a good bet that you want to use the subjunctive mood.
And another example:
Then we are using the subjunctive mood ("you be") because this is a mandative statement (note that the imperative is something else, grammatically).
In any discussion of the subjunctive mood in English, it is worth noting that this particular grammatical construction is often morphologically identical to the normal indicative, showing up only with "be" and in constructions involving third person (historically, this was not the case). Perhaps as a result, the subjunctive mood as something with overt morphological markings is disappearing from English. (That is not to say that the subjunctive mood would cease to exist if the distinguishing morphology disappeared — it would still be there whether it looks different from other constructions or not.)
Because the overt subjunctive is disappearing, you often see it looking like normal past tense: "if I was ten years younger". At the moment, this remains nonstandard, but common.
I'll just quote the Encarta encyclopedia, since I believe the rule it mentions is different from what the answers mention.
Specifically, note the part that says "however remote", which I did not seem to see in the other answers. (This is different from how the subjunctive is used in languages such as French, where it is merely used to express doubt.)
Well, the above answer is very close. I mean, to be all honest, the subjunctive isn't dead in Modern English. You probably say it all of the time and don't know it. Technically, in all honesty, when one says something like, "If he only knew what I had done, he would kill me", the verb "knew" in "he knew" is technically 3rd person singular past subjunctive of the verb "to know", but it looks the same as the past indicative in Modern English. Another example:
"If I had had more time, I would have done it."
The above "I had had" is the past perfect subjunctive, but it looks just like the past perfect indicative so the subjunctive is there; its just hard to see these days. Although, if one were to say (future subjunctive) something like, "If I were king of England, I would cut taxes", he would be using a subjunctive conjugation with a morphological inflection that differs from the past indicative "I was".
Technically, we used to use the morphological present subjunctive in Modern English after conjunctions like "if, whether, unless, until, before, although, though, lest, etc.", but, nowadays, this is rarely seen or heard and many consider it pretentious to use it, but it's still correct. Here's an example:
"If music be the food of love, play on." (Shakespeare)
We can see this in "if truth be told", "whether it be", "until death do us part", and so on wherein the verb is in the subjunctive form. These above statement are still said in English. Below, I shall show the indicative/subjunctive conjugations in English for the verbs "to be" and "to speak":
Present Ind./Subj. He is/He be He speaks/He speak
Past Ind./Subj. He was/He were He spoke/He spoke
Future Ind./Subj. He will be/He were to be He will speak/He were to speak
Past Perfect Ind./Subj. He had been/He had been He had spoken/He had spoken
Present Perfect Ind./Subj. He has been/He have been He has spoken/He have spoken
There are more conjugations, but these are the most common ones. I'm not going to go into how to use them in detail per se because that has already been shown to you in the original answer. Here are the conjugations, though. I hope this might help.
Thank you for your interest in this question.
Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.
Would you like to answer one of these unanswered questions instead?