Verb forms and combinations can demonstrate a number of things. Most commonly in Western languages they are marked for “tense” (when something occurs), “aspect” (whether something is complete or progressive) and, perhaps most mysteriously for English speakers, “mood”.
“Mood” is tricky, because it can mark a huge range of things depending on the language (and, arguably, underlying culture). In the case of languages closest to English speakers (Germanic languages like German or Dutch, or Latinate languages like French or Spanish), the most common issue is that of the “subjunctive mood”, typically used to express something which is counterfactual, hypothetical or assumptive.
The subjunctive mood is in decline in almost every one of those languages, particularly in spoken use. It is hard to measure precisely, but the problem arises because it has probably declined further in English (and, specifically, British English).
Firstly, the subjunctive does have a common use in all languages as a means of expressing a desire, particularly in set phrases: “Long live the Queen!” is also subjunctive in French (“Vive la reine!”; also commonly “Vive la France!“), Spanish (“¡Viva la reina!”; also commonly “Viva España”), and German (“Hoch lebe die Königin!”) among others, including actually Esperanto (“Vivu la regxino!“).
Secondly, however, its usage, particularly in contemporary speech, varies hugely otherwise. In Spanish and (even more so, perhaps) Italian, it is a constant feature of the daily language, particularly in subordinate clauses (usually introduced in Spanish by que and Italian by che, although not all of these require the subjunctive). The subjunctive is compulsory to indicate objective, often translated by the infinitive (“to be”, “to do”, “to like” etc):
La LFP enviará entrenadores españoles a China para que trabajen en colegios – “The LFP [football league] will send Spanish coaches to China to work in colleges.” [El Periódico, 4 August 2015]
It is also used to indicate desire or obligation:
Espero que vengas a visitarnos – “I hope you come to visit us” [Word Reference, 19 August 2015]
Hay que tú lo hagas – “It is necessary that you do it” [RTVE Text, 18 August 2015]
It can indicate hypothesis, including in very broad terms:
Lo importante es que te guste a tí – “The important thing is that you like it” [Coca Cola advert, RTVE, February 1998]
It can also mark something which is clearly counterfactual, effectively changing the meaning of an introducing phrase:
Aunque sea bueno, no le seleccionan – “Even if he is good, they don’t select him” [subjunctive]
Aunque es bueno, no le seleccionan – “Even though he is good, they don’t select him” [not subjunctive]
In Spanish, the present subjunctive is also used to indicate uncertainty in the future (other languages often use a future tense here):
Hasta que salga el sol – “Until the sun goes out” [song title, Don Omar, 2012]
Again, there is a distinction in meaning here:
Lo hacemos cuando vienes – “We do it when you come” [i.e. habitually]
Lo haremos cuando vengas – “We’ll do it when you come” [i.e. once, in future]
Away from subordinate clauses, it can also indicate generalisation, again changing the meaning of the introducing word:
Gane quien gane – “Whoever wins, wins” / “I don’t care who wins” [both subjunctive]
Closest to English, there is also a past subjunctive (actually with two different forms used more or less interchangeably, but we’ll not go into that…) used to indicate hypothesis, particularly in conditional clauses:
Si yo fuera rico – “If I were a rich man” [translation of song title]
Numerous verbs are also followed by the subjunctive only in the negative or interrogative (as this expresses a counterfactual situation, whereas the positive does not):
Creo que lo sabes / No creo que lo sepas / ¿Crees que lo sepa yo? – “I believe you know / I don’t believe you know / Do you believe I know?”
Spanish also theoretically has a future subjunctive, although this is now restricted to literary or legal usage (not so in Portuguese, in fact, where it is still heard in speech).
French in theory uses the subjunctive in much the same way as Spanish. However, in daily speech, it often manages without the subjunctive, except for more formal situations or particular phrases.
Obligation takes the subjunctive, even typically in daily speech:
Il faut que tu le fasses – “It is necessary that you do it”
However, desire is less certain:
J’espère que tu viens [or viennes] rendre visite – “I hope you come and visit” [not subjunctive, at least in common parlance – there is uncertainty even among native speakers about such cases]
French typically does distinguish between the positive (factual) and negative (counterfactual), as with Spanish above:
Je crois que tu le sais / Je [ne] crois pas que tu le saches / Crois tu que je sache? – “I believe you know / I don’t believe you know / Do you believe I know?”
Unlike Spanish, French uses the future in clauses with “when”:
Nous le ferrons quand tu arriveras – “We will do it when you come”
German, however, not being Latinate, uses the “subjunctive” (often known as “conjunctive”) is a completely different way, most markedly to express “reported speech”:
Frau Merkel habe besondere Vorteile in der seinerzeitigen DDR genossen – “[It is said that] Ms Merkel enjoyed special privileges in the East Germany of the time / Ms Merkel [reportedly] enjoyed special privileges in the East Germany of the time” [Chronik Berlin, 2005]
There are also particular set usages to indicate something obviously counterfactual:
Er guckte mich an, als käme ich von einem anderen Stern – “He looked at me as if I came [from the moon]”
There are also mixed conditional usages which may or may not be deemed “subjunctive”. However, unlike Spanish, Italian and (formal) French, there is no subjunctive for wish or desire:
Ich hoffe, dass du besuchen kommst – “I hope you come to visit” [no subjunctive]
So, what about English? I touched on it in the second half of this article, which I recommend you read. Ahem, see what I did there? “Read” is in fact subjunctive in that sentence…
The subjunctive is used in English more often than we sometimes believe, but in many cases (such as the last paragraph) its form is the same as it would be otherwise and therefore we do not notice. However, if we change this to “which I recommend she read”, or even “which I recommend be read”, we can see the subjunctive form.
This can be critical. Compare “He insists she pays” with “He insists she pay”; the first means that he is insistent that she (habitually) pays; the second that he was insistent that she pay in a particular instance.
Of course this is, as in French, a formal thing – in modern speech “He insists she pays” is the more likely form with the distinction left to context.
As in German, the subjunctive of desire is largely lost, although there are vestiges in the use of past subjunctive forms after certain verbs or in set phrases (“Wish you were here”, “Would that they had” – both present meaning, actually subjunctives).
Modern English also gets around subjunctives, either by other modal verbs (“I will carry out his recommendations, whatever they may be”) or, arguably, by the infinitive (“I want you to be there”).
So, thirdly, if English largely gets by without the subjunctive, surely languages could just do away with it? It seems this is not so easy. If this were the case, for example, you certainly would not complicate an invented language designed to be regular with a subjunctive. Yet one exists in Esperanto, with usage somewhat akin to French (even if it is seen as more optional than complisory in some instances).
Necesas, ke vi faru gxin – “It is necessary that you do it” [optional subjunctive]
Mi esperas, ke vi venos viziti – “I hope you come to visit” [subjunctive generally not used]
Fundamental distinctions in meaning can be illustrated by the subjunctive, even in Esperanto:
Mi diris al vi, ke vi iros Belfaston – “I told you you would go to Belfast” [not subjunctive, statement of fact]
Mi diris al vi, ke vi iru Belfaston – “I told you to go to Belfast” [subjunctive, statement of command (but possibly not fact)]
In conclusion, the subjunctive mood has wildly varying usages and is in wildly different states of decline in the major European languages. Yet even in English, the world language where that decline is perhaps most marked, it remains in use; and even in Esperanto, an invented language set up to be regular and uncomplicated, it has a clear role.