Conditions in Ancient Greek
Conditional statements are sentences which represent a relationship between two clauses whereby the veracity of one clause depends on a circumstance expressed by the other. The ideas expressed by each clause may be understood to be true or hypothetical.
Every complete conditional sentence contains a protasis and an apodosis. The protasis is a dependent the expressing a condition, and the apodosis is an independent clause expressing the consequence. In the English sentence “If you seek, you shall find,” “If you seek” is the protasis, and “you shall find” is the apodosis. Protasis and apodosis can occur in either order without changing their function, so the sentence “You shall find if you seek” has the same protasis and apodosis as the sentence above, even though their order is reversed.
In Classical Greek, protases are introduced by either ἐάν or εἰ, which mean “if.” Negation in the protasis requires μή; in the apodosis, οὐ.
Protasis: ἐάν + subjunctive
Apodosis: future indicative, δεῖ + infinitive, or imperative
Expresses a very likely outcome after the fulfillment of the condition
Example: ἐὰν ἔλθῃ, πεῖθε αὐτόν. “If he comes, then persuade him!”
Present general (or present indefinite)
Protasis: ἐάν + subjunctive
Apodosis: present indicative
Expresses a certain outcome in the present always occurring at the same time as the condition
Example: ἐὰν χρήματα ἔχῃς, φίλους ἔχεις. “If you have money, you have friends.”
Expresses a less likely outcome after the fulfillment of the condition
Example: εἰ ἀκούσαι, πείσαιμεν ἂν αὐτόν. “If he were to listen, we would persuade him.”
Past general (or past indefinite)
Apodosis: imperfect indicative
Expresses a certain outcome in the past always occurring at the same time as the condition
Example: εἰ χρήματα ἔχοις, φίλους εἶχες. “If you had money, you had friends.”
Protasis: εἰ + indicative
Apodosis: indicative or imperative
Expresses that the outcome is a logical consequence of the condition, whether or not the condition is fulfilled
Example: εἰ ὁ στρατηγὸς σοφὸς ἦν, οὐκ ἐπίστευσε τῷ ἡγεμόνι. “If the general was wise, he did not trust the guide.”
Protasis: εἰ + past indicative
Apodosis: ἄν + past indicative
Imperfect verbs refer to the present; aorist verbs refer to the past
Expresses an outcome that would have occurred if the condition had also been fulfilled (even though it was not)
Example: εἰ μὴ κατελύσαμεν τοὺς Πέρσας, δοῦλοι ἂν ἦμεν. “If we had not destroyed the Persians, we would be slaves.”
Conditions in indirect discourse
Any type of condition from the above can be put into an indirect statement
Protasis: if the verb of speaking is in a primary tense, unchanged; if it is in a historic tense, the optative may optionally be used
Apodosis: if ὅτι or ὡς is used, then the rule for the protasis is followed; if not, the infinitive or participle has the same tense as the verb in direct speech; ἄν is always retained
Example: ἔφη, εἰ ἥμαρτεν, ἀποθανεῖν ἄν. “He said that if he had made a mistake, he would have been put to death.”
For more, see: C. W. Shelmerdine, Introduction to Greek; M. A. North, A. E. Hillard, Greek Prose Composition for Schools.
(Examples are from Shelmerdine, except for examples in indirect discourse, which are from North and Hillard.)