In both English and German, there are tenses and there are moods. We use the indicative mood to state facts, the imperative mood to give commands, and the subjunctive mood to reflect wishes or actions in unreal situations ("I wish I were taller" or "I would travel around the world."). Take a look at this past newsletter for information on the formation of the subjunctive (Konjunktiv) in German. The subjunctive is a key part of conditional sentences that describe levels of possibility, from events that are very likely to missed opportunities in the past.
Type 1 conditional sentences refer to cause-and-effect links, and events that are quite certain under particular circumstances. Because German sentences often use the present tense to imply the future, the basic structure is wenn or falls (see this newsletter) followed by the present tense, like in English, but then it can be followed by either the present tense or future constructed with werden.
Wenn es so weitergeht, werden bis 2050 drei Viertel aller Alpengletscher verschwunden sein... mit gewaltigen Folgen.
If it continues this way, by 2050, three quarters of all the alpine glaciers will have disappeared ... with enormous consequences.
Caption 33-34, Alpenseen: Kühle Schönheiten
Type 2 conditional sentences refer to events that are less possible or likely, often hypothetical. Its structure in German is Wenn + Konjunktiv II + Konjunktiv II.
Wenn immer Sommer wäre, würde ich jeden Tag grillen.
If it were always summer, I would grill every day.
Caption 29, Konjugation: Das Verb „grillen“
Wenn ich viel Geld hätte, würde ich nie wieder arbeiten gehen.
If I had a lot of money, I would never go to work again.
Caption 23, Konjugation: Das Verb „gehen“
Ich denke, wenn ich weniger arbeiten würde, könnte ich mich mehr konzentrieren.
I think that if I worked less I could concentrate better.
Caption 34-35, Berufsleben: Probleme mit Mitarbeitern
Type 3 conditional sentences are used to talk about possibilities or events that never came to be. Here is where the structure gets a bit complicated. In its full form, the construction is Wenn + participle + Konjunktiv II + Konjunktiv II + participle.
Wenn wir eine Chance gehabt hätten, dann wären wir vorher gegangen, ja.
If we had had a chance, then we would've left before, yes.
Caption 34, Die Klasse: Berlin '61
Ja, wenn Jannik fit gewesen wäre, dann wäre er nie runtergekracht.
Yes, if Jannik had been healthy, then he wouldn't have ever gone crashing down.
Caption 59, Großstadtrevier: Von Monstern und Mördern
It is worth mentioning that you may often see "mixed types" of the conditional, in which a missed opportunity in the past (expressed using the participle) is portrayed as still affecting the present. Take a look at the following sentence:
Also, wenn wir den Vertrag letzte Woche unterzeichnet hätten, wären wir in der Lage, mit unserer ursprünglichen Vereinbarung fortzufahren?
So, if we had signed the contract last week, we would be in a position to proceed with our original agreement?
Caption 36-37, Berufsleben: Probleme mit Mitarbeitern
For more information on the different types of conditional sentences, take a look at this helpful website. Whenever you see key words like hätte, wäre, or würde on Yabla German, note the subjunctive mood and try to identify which type of conditional sentence it might be related to.