This is the house where he was murdered.
How is adverb “where” modifying the verb “was murdered”? It doesn't seem to be behaving like an adverb.
This is the house where he was murdered.
How is adverb “where” modifying the verb “was murdered”? It doesn't seem to be behaving like an adverb.
First off, the verb in this sentence is not 'was murdered'; it's 'is'.
"This is the house" is the basic subject-verb-object structure of the sentence.
The word 'where' serves as a conjunction linking the phrase 'he was murdered' to the noun 'house'.
See conjunction definition 3 of 'where' at MW, which includes an example that's parallel to your sentence.
at, in, or to which place 'the town where she lives'
"This is the house where he was murdered" is a complex sentence. In addition to the main clause (which as John Feltz says has the same structure as the simple sentence "This is the house"), it contains a dependent clause: the relative clause "where he was murdered", which modifies "the house".
The internal structure of the relative clause "where he was murdered" seems to be the same as that of the sentence "He was murdered there". (These two clauses have different word orders because wh-words like "where" are "fronted" in various contexts in English.)
The function of "there" in a sentence like "He was murdered there" seems to be the same as the function of a prepositional phrase in a sentence like "He was murdered in that house". Prepositional phrases used like this are sometimes termed "adverbial phrases" or "adverb phrases".
So, where in this sentence is a single word that functions like the "adverb phrase" "in that house", which I think is why it may be called an "adverb". My understanding is that other terminological systems use the word "adjunct" to refer to the same function. Related ELL question: Why is 'where' an adverb and not a pronoun?
A number of terminological systems for describing English grammar exist, and I have the impression that "where" is not always categorized as an adverb. Its behavior is more similar in some respects to that of a preposition, or in other respects it is similar to a pronoun (in this case, a relative pronoun). I had forgotten before reading John Feltz's answer that it can also be seen as a conjunction; some previous questions that discuss this are A relative adverb or a conjunction or both? and "Where" as a conjunction.