La concordance des temps au subjonctif
Classical French had four subjunctive tenses: présent, passé, imparfait du subjonctif, and plus-que-parfait du subjonctif. The last two — the literary subjunctives — have all but disappeared from spoken and modern written French. In practice, everyday French uses only two: subjonctif présent for simultaneous/future events, and subjonctif passé for anterior events. The literary forms survive in 19th-century novels, formal speeches, and a few stock expressions. You need to recognize them when reading classical literature, but you should never produce them in normal speech or writing — modern French uses the present and past subjunctive even when the main verb is in the past.
The everyday system — only two tenses
Modern French has collapsed the old four-tense subjunctive into a two-way system based purely on whether the subordinate event is simultaneous/future (→ subjonctif présent) or anterior (→ subjonctif passé) relative to the main verb. The tense of the main verb does not matter. Je veux qu'il vienne. = I want him to come. Je voulais qu'il vienne. = I wanted him to come. J'ai voulu qu'il vienne. = I wanted him to come. In all three, the subordinate verb stays in the subjonctif présent because coming is simultaneous-or-future relative to wanting. Compare: Je suis content qu'il soit venu. / J'étais content qu'il soit venu. = I'm glad / I was glad he came. The subjonctif passé stays the same because coming is anterior in both cases.
What the classical sequence used to require
Classical French used to demand a fuller sequence of tenses: when the main verb was in the past or conditional, the subordinate subjunctive shifted backwards. The old rule produced four pairings: (1) main present/future + simultaneous → subjonctif présent; (2) main present/future + anterior → subjonctif passé; (3) main past/conditional + simultaneous → imparfait du subjonctif; (4) main past/conditional + anterior → plus-que-parfait du subjonctif. Modern French has thrown out (3) and (4) entirely. Where Voltaire wrote Je voulais qu'il vînt, today we say Je voulais qu'il vienne. Where Hugo wrote J'aurais voulu qu'il fût venu, today we say J'aurais voulu qu'il soit venu.
L'imparfait du subjonctif — recognition only
Formed from the passé simple: take the tu form of the passé simple, drop the final -s, and add -sse, -sses, -ˆt, -ssions, -ssiez, -ssent. parler → que je parlasse, que tu parlasses, qu'il parlât, que nous parlassions, que vous parlassiez, qu'ils parlassent. être → que je fusse, que tu fusses, qu'il fût…. avoir → que j'eusse, que tu eusses, qu'il eût…. The famous circonflexe on the il form (qu'il vînt, qu'il fût, qu'il eût) is the giveaway. You will see this in 19th-century novels (Flaubert, Hugo, Balzac) and in deliberately formal/literary writing. You should not use it. It sounds either pompous or accidentally comedic in modern French.
Le plus-que-parfait du subjonctif — recognition only
Formed by putting avoir or être in the imparfait du subjonctif, then adding the past participle. qu'il eût parlé, qu'il fût venu, qu'elle se fût levée. Used in the most formal classical prose to mark anteriority in a past frame, where modern French uses the subjonctif passé. It also has a second life as a literary substitute for the conditionnel passé: Il eût voulu rester = Il aurait voulu rester = He would have wanted to stay. Again — recognize it, do not produce it. If you write qu'il eût parlé in a modern email, you will sound like a parody of a 19th-century novelist.
Modern register — written vs spoken
The collapse to the two-tense system is now near-total in spoken French and in nearly all written registers. Even in formal writing — academic essays, legal prose, journalism — the subjonctif présent and subjonctif passé are the standard. The literary subjunctives appear in: (a) literature pre-1950; (b) deliberate stylistic archaism; (c) a handful of fixed expressions like plût à Dieu ('would to God', literary). One small exception: fût-ce ('even if it be') survives in slightly elevated writing — Je viendrai, fût-ce sous la pluie. = I'll come, even if it's raining. Outside of those, you can safely use only subjonctif présent + subjonctif passé, regardless of the tense of the main verb.
Quick recap
(1) Modern French uses only two subjunctive tenses: présent for simultaneous/future events, passé for anterior events. (2) The tense of the main verb does NOT change which subjunctive you use. (3) Imparfait du subjonctif (qu'il vînt, qu'il fût) and plus-que-parfait du subjonctif (qu'il eût parlé) are recognition-only — read but don't write. (4) When in classical texts you see qu'il fût or qu'il eût parlé, mentally translate to qu'il soit and qu'il ait parlé.
