Complex clauses serve to describe conditions and their consequences ("if ..., then ...").
A conditional construct is generally comprised of:

• the subordinating clause (the actual conditional clause), which contains the condition (Protasis, céadbheart) and
• the main clause, which describes the consequence of the condition (Apodosis, iarbheart)

The order of main- and subordinating clause is random in Irish (as in German).
In Irish one differentiates between two forms of conditional clauses, real and irreal:

the real conditional clause (an clásal coinníollach oscailte)

• the condition is / would be/ will be fulfilled
• the condition is attainable
• the condition is probable, to be fulfilled.

• indicative, imperative or subjunctive present tense, less commonly also in the conditional

• the indicative and is introduced with má, mura(r).
  after má the future tense never follows, instead the (habit.) present tense

Má requires lenition. The independent verb form is used (i.e. in the preterite one needs the d'-prefix).

Negative clause: (If not...)
 

mura requires eclipsis and the dependent verb form.
murar requires lenition
After mura one can also use the subjunctive present tense (in the future sense).

regional also: mara, marar or muna, munar

The irreal conditional clauses use the same conjunction (mura), but then either the subjunctive preterite or conditional and not the indicative. Murar appears only in real conditional clauses.

the irreal conditional clause (an clásal coinníollach iata)

• the condition is not attainable
• it is sure, that the condition will not/could not be fulfilled
• there is a reasonable doubt about the attainability of the condition.
• in indirect speech, the real conditional clause (if in the future tense) is converted into an irreal conditional clause.

• conditional

• either in the conditional or in the subjunctive preterite and is introduced by dá, mura.

• Dá requires eclipsis and the dependent verb form.
• The subjunctive preterite has the identical form as the imperfect.
• Dá-clauses with the subjunctive preterite (rather old fashioned) and the conditional are lexically equivalent
• Irreal conditional clauses are indifferent in tense ("If you would see the man / had seen the man ")

Negative clause: ("if/then not ...")
 

• mura requires eclipsis.
• mura with the subjunctive is generally seen as archaic, but was probably the original form
• in place of the subjunctive preterite one can take the conditional (the most common form today)

The real conditional clauses use the same conjunction (mura), but after that, then not the subjunctive/conditional but the indicative (present tense etc.) or murar with the indicative preterite.

complex conditional clauses (clásail choinníollacha iolracha)

If more than one condition is to be fulfilled (real or irreal) , then:

• only the first condition contains má, dá, mura with a finite verb form (see above)
• further conditions are conjoined with agus and stand as infinitive constructions with the verbal noun