Subjunctive

Subjunctive mood
In grammar, the subjunctive mood is a verb mood typically used in dependent clauses to express wishes, commands, emotion, possibility, judgment, opinion, necessity, or statements that are contrary to fact at present. It is sometimes referred to as the conjunctive mood, as it often follows a conjunction. The details of subjunctive use vary from language to language.
•   
[edit] The subjunctive in Indo-European languages
The reconstructed Proto Indo-European language is the hypothetical parent of many language families. These include the Romance languages, Celtic languages, Germanic languages (including English), Slavic languages, many of the languages of the Indian subcontinent and the Iranian or Persian languages and several others. It had two closely related moods: the subjunctive and the optative. Many of its daughter languages combined or merged these moods.
In Indo-European, the subjunctive was formed by using the full ablaut grade of the root of the verb, and appending the thematic vowel *-e- or *-o- to the root stem, with the full, primary set of personal inflections. The subjunctive was the Indo-European irrealis, used for hypothetical or counterfactual situations.
The optative mood was formed with a suffix *-ieh1 or *-ih1 (with a laryngeal). The optative used the clitic set of secondary personal inflections. The optative was used to express wishes or hopes.
Among the Indo-European languages, only Albanian, Avestan, Ancient Greek, Sanskrit, and to some extent Old Church Slavonic kept the subjunctive and optative fully separate and parallel. However, in Sanskrit, use of the subjunctive is only found in the Vedic language of earliest times, and the optative and imperative are in comparison less commonly used. In the later language (from c.500BC), the subjunctive fell out of use, with the optative or imperative being used instead. However, the first person forms of the subjunctive continue to be used, as they are transferred to the imperative, which formerly, like Greek, had no first person forms.
[edit] The subjunctive in English
[edit] Form
[edit] Modern Form
The subjunctive in Modern English is easily distinguished in a great variety of contexts where the sense is past tense, but the form of the subjunctive verb required is present: "It was required that we go to the back of the line". Were it not for the subjunctive, the form of "to go" for something in the past would be went. Compare with the indicative, "Everyone knows that we went to the back of the line".
    Present indicative    Present subjunctive    Past indicative    Past subjunctive
to own
(regular verb)    I own
he/she/it owns
we/you/they own    I own
he/she/it own
we/you/they own    I owned
he/she/it owned
we/you/they owned    I owned
he/she/it owned
we/you/they owned
to be    I am
he/she/it is
we/you/they are    I be
he/she/it be
we/you/they be    I was
he/she/it was
we/you/they were    I were
he/she/it were
we/you/they were
As shown in the above table, the form of the subjunctive is distinguishable from the indicative in only three circumstances:
1.    in the third person singular of the present tense,
2.    with the verb to be in the present tense, and
3.    in the first person singular and third person singular of verb to be in the past tense.
The modal auxiliaries do not have present subjunctive forms.
In Early Modern English, the past subjunctive was distinguishable from the past indicative not only in the verb to be (as in Modern English) but also in the second-person singular of all verbs. For example: indicative thou sattest, but subjunctive thou sat.
Nevertheless, in some texts in which the pronoun thou is used a final -est or -st is sometimes added; for example, thou beest appears frequently in the work of Shakespeare and some of his contemporaries.
[edit] Present and past subjunctive
The terms present subjunctive and past subjunctive can be misunderstood, as they describe forms rather than meanings: the past and present subjunctives are so called because they resemble the past and present indicatives, respectively, but the difference between them is a difference in modality, not a temporal one.
For example, in "I asked that it be done yesterday," be done (a present subjunctive) has no present-tense sense; and likewise, in "If that were true, I would know it," were (a past subjunctive) has no past-tense sense.
To give another example, "It is high time that we bought a new car". Although bought appears to be the past tense of the verb to buy, actually the car has not been purchased yet. Here, the past subjunctive is used to express a wish or a suggestion.
[edit] The pluperfect subjunctive
Since the "past subjunctive" is not a true past tense, it uses as its past tense what is structurally its perfect aspect form. This past tense is known as the past perfect subjunctive or pluperfect subjunctive; it is formed using had (the past subjunctive of to have) plus the verb's past participle.
The pluperfect subjunctive is used like the past subjunctive, except that it expresses a past-tense sense. So, for example:
•    If I had known (yesterday), I would have done something about it.
•    If I had seen you, I definitely would have said hello.
•    I would not be here if he had not helped me.
When used in the construction of a counterfactual statement as in the examples above, it is paired with the conditional perfect viz. "If I had [not] X, then I would [not] have Y". The (arguably) canonical example of the counterfactual actually eschews the pluperfect subjunctive: "If I Knew You Were Comin' I'd've Baked a Cake".
If a clause is in a past tense, then a clause subordinate to it cannot be in the past subjunctive, though it might be in the pluperfect subjunctive; however, if it is in a present tense, then a clause subordinate to it might be in either of the two, depending on meaning.
The pluperfect subjunctive is often replaced with the past subjunctive in colloquial speech, a substitution that is commonly considered incorrect. (See prescription and description.)
(Note that by contrast, the present perfect subjunctive — that he have done — while logically and theoretically possible, is not much used in modern English.)
[edit] Future subjunctive
A future subjunctive can be constructed using the conjugated form of the verb "to be" plus the infinitive or with the usage of the modal auxiliary verb "should". Note that the "were" clauses result in the present conditional, while the "should" clauses result in the future indicative. For example:
•    If I were to die tomorrow, then you would inherit everything.
•    If you were to give the money to me, then I would say no more about it.
•    If I should go, then will you feed the hens?
•    If he should fall, who will carry the flag in his place?
[edit] Construction by inversion
Where the subjunctive is used after "if" in a counterfactual condition (see below), the same effect can be achieved by omitting the "if" and containing the verb and subject.
•    If I were the President... / Were I the President...
•    If he had a car with him... / Had he a car with him...
[edit] Set phrases
The subjunctive is used in a number of fixed phrases, relics from an older form of the language where it was much more common. Some could be misconstrued as the imperative mood. Common examples are:
•    if need be
•    as it were
•    if I were you; were I you
•    be that as it may
•    (God) bless you!
•    come Monday (Tuesday, etc.)
•    come what may
•    far be it from (or for) me
•    until death do us part
•    God save our gracious Queen, God bless America, God keep our land glorious and free, God rest ye merry gentlemen, etc.
•    Heaven forfend/forbid
•    so be it
•    suffice it to say
•    woe betide
•    peace be with you
•    long live the king
•    the powers that be
•    albeit (a synthesis of all be it, i.e. although it be)
•    truth be told
•    rue the day
•    would that it were
•    rest in peace
•    let (may) it be known
•    ...need only...
•    May the best man win
"May the best man win" is an example of the subjunctive. If may were used as a modal such as in "the best man may win", this would not be the subjunctive. Other Indo-European languages use the subjunctive in this same form such as in Spanish "que les vaya bien" (lit. may you go well) and "que sea de alta prioridad" (lit. may it be of high priority). The subjunctive is used in this formula in Spanish just as it is in English.
. http://en.wikipedia.org/wiki/Subjunctive