In German, relative clauses are usually introduced by the relative pronouns der, die, and das, which agree in gender, number, and case with their antecedent. These pronouns are declined like definite articles and connect two clauses by referring back to a specific noun. For example, Das ist der Mann, der das Auto fährt ("That is the man who drives the car") shows how der refers directly to der Mann and functions as the subject of the relative clause. This system works smoothly with concrete nouns. However, German also uses was, wo, and wer as relative elements when standard relative pronouns are less natural or don’t apply.
The word was functions as a relative pronoun when it refers to indefinite or abstract antecedents, especially neuter pronouns or general words like alles (everything), etwas (something), nichts (nothing), viel (much), or wenig (little). For example, Nichts, was er sagt, interessiert mich translates as "Nothing he says interests me." Here, was connects nichts to the clause explaining what does not interest the speaker. Was is invariable and does not show case, so the role of subject or object is made clear within the relative clause itself. Was can also refer to an entire previous statement, as in Sie ist gegangen, was niemand erwartet hatte ("She left, which no one had expected"). In this case, was refers to the act of leaving rather than a specific noun.
The word wo serves as a relative adverb and often replaces prepositional phrases that express location, time, or even abstract spaces or situations. Wo is common in spoken German and informal writing, sometimes sounding more natural than constructions like in dem or an dem. For instance, Das Café, wo wir gestern waren, hat gute Kuchen means "The café where we were yesterday has good cakes." Here, wo introduces the relative clause describing the café.
In colloquial usage, wo is also used to replace prepositional phrases related to time, place, or context. An example is Der Moment, wo alles still wurde, war unheimlich ("The moment when everything went silent was eerie"), where wo substitutes for in dem or zu dem. Similarly, Die Gegend, wo er arbeitet, ist sehr teuer translates as "The area where he works is very expensive," taking the place of the more formal in der er arbeitet. Another example is Ich suche eine Wohnung, wo ich einen Balkon habe ("I’m looking for an apartment where I have a balcony"), which would be more formal as in der ich einen Balkon habe. This use of wo streamlines the sentence and is widespread in everyday speech, especially when the relative clause involves a location or situation rather than a specific object. Even abstract references follow this pattern, as in In der Kultur, wo er aufgewachsen ist, ist Pünktlichkeit sehr wichtig ("In the culture he grew up in, punctuality is very important"). In formal writing, these sentences might use in der instead, but wo keeps them conversational and natural.
The relative pronoun wer introduces clauses without a specific antecedent and is best translated as "whoever" or "anyone who." It is used when the subject is unknown or general. For instance, Wer das versteht, ist wirklich klug means "Whoever understands that is truly smart." Wer combines the role of both the antecedent and the relative pronoun, and its case changes within the relative clause depending on its grammatical role. Another example is Wer helfen möchte, kann sich melden ("Anyone who wants to help can get in touch"), where wer introduces a general condition rather than referring back to a specific noun.