USES OF SUBJUNCTIVE MOOD
A) INDIRECT QUESTIONS
In indirect question the verb has person and the mood of the original verb changes from the indicative to the subjunctive.
Estne callida? (Is she clever?) ->
Rogat num callida sit. (He asks whether she is clever.)
Rogavit num callida esset. (He asked if she was clever.)
Cur venis? (Why are you coming?) ->
Nescio cur venias. (I don't know why you're coming.)
Veniuntne nostri amici? (Are our friends coming?) ->
Rogat veniantne nostri amici. (He is asking whether our friends are coming.)
Quanta pericula sunt? (How great are the dangers?) ->
Video quanta pericula sint. (Now I see how great the dangers are.)
When the indirect question is depicting an event that is conceived of as contemporaneous with the action of the main verb, then:
i) subordinate verb in subjunctive present,
Nescio quid facias? (I don't know what you're doing.)
Rogat veniantne nostri amici. (He asks whether our friends are coming.)
ii) subordinate verb in subjunctive imperfect
Nescivi quid faceres? (I didn't know what you were doing.)
Rogaverunt venirentne nostri amici? (They asked whether our friends were coming.)
When the indirect question is depicting an event that is conceived of as having been undertaken before the action of the main verb, then:
i) subordinate verb in subjunctive perfect
Nescio quid feceris. (I don't know what you did.)
Rogat venerintne nostri amici. (He asks whether our friends came.)
ii) subordinate verb in subjunctive pluperfect
Nescivi quid fecisses. (I didn't know what you had done (or did).)
Rogaverunt venissentne nostri amici. (They asked whether our friends had come (or came).)
time subsequent (after):
When the indirect question is depicting an event that is conceived as coming after the action of the main verb, then:
i) subordinate verb in active future participle + esse in subjunctive present
Nescio quid facturus sis. (I don't know what you will do (you're going to do).)
Rogat sintne venturi nostri amici. (He asks whether our friends will come (are going to come).)
ii) subordinate verb in active future participle + esse in subjunctive imperfect
Nescivi quid facturus esses. (I didn't know what you were going to do (would do).)
Rogaverunt essentne venturi nostri amici. (They asked whether our friends were coming (would come).)
B) THE JUSSIVE SUBJUNCTIVE
The only use of the subjunctive in the main clause of a sentence is the jussive subjunctive. It is used when a command or exhortation is directed to a first or third person. To issue a prohibition or negative command in the first or third persons, the negative particle "ne" is used.
Viros bonos laudamus. (We are praising good men.) ->
Viros bonos laudemus. (Let's praise good men.)
Veniunt. (They are coming.) ->
Veniant. (Let them come.)
Libros malos non legimus. (We don't read bad books.) ->
Ne libros malos legamus. (Let's not read bad books.)
C) SUBORDINATE CLAUSES
Subjunctive is mainly used in subordinate clauses.
1) PURPOSE clauses, often introduced by ut "in order that" or ne "in order that not."
Venerunt ut reginam adiuvarent. (They came in order to help the queen.)
2) RESULT clauses introduced by ut "with the result that" or ut non "so that not."
Servus ade callidus est ut non lab ret. (The slave is so clever that he doesn't work.)
3) CAUSAL clauses introduced by cum "since."
Cum audire non possent, cives excesserunt. (Since they couldn't hear, the citizens went away.)
4) CIRCUMSTANTIAL clauses introduced by cum "when" with a past tense verb.
Cum cives convenissent, tropaeum viderunt. (When the citizens had assembled, they saw the victory monument.)
5) CONCESSIVE clauses introduced by cum "although." Cum sit senex, tamen discere potest. (Although he is an old man, he is able to learn.)
6) Clauses of FEARING introduced by ne "lest/that" or ne non or ut "that... not."
Timeo ne hostis veniat. (I am afraid that the enemy may come.)
Timeo ut amicus veniat. (I am afraid that my friend may not come.)