I am confused. When should the conditional subjunctive and the conditional indicative be used?
Conditional subjunctive:
If you were 23 yrs old, you could join the contest.
Conditional indicative:
If you are 3=23 yrs old, you can join the contest.
A follow up: In the conditional subjunctive, should the second verb be in the past tense?
Your first sentence is an example of what is sometimes taught to foreign learners as the Second Conditional, which envisages an unreal, unlikely or imagined situation. In these sentences, the verb in the if-clause is in the past tense. The verb phrase in the main clause is usually made up of would followed by the plain form of the main verb, but other modals such as could are also found.
Your second sentence is an example of the First Conditional, which predicts a likely result in the future if the condition is fulfilled. Its typical structure is present tense in the if-clause and will (or won’t) in the main clause, but can is also possible.
The term 'conditional subjunctive' is not normally used.
