The preposition commonly used before "world" in English is "in." For example, "the world in which we live." This preposition is chosen because it signifies inclusion or a specific context within which the world is being discussed. The use of "in" is supported by linguistic data and conventions in English grammar.

Linguistic studies have consistently shown that "in" is the most frequent preposition used with "world" in English. According to the Corpus of Contemporary American English (COCA), "in the world" is the most common collocation, followed by "of the world" and "the world of." The COCA is a large and continually updated database of American English, providing a reliable source for such linguistic analysis. The prominence of "in" in these collocations suggests that it is the preferred preposition when referring to the world in a general or abstract sense.

The choice of "in" over other prepositions like "on," "at," or "with" is also influenced by the semantic field of the word "world." "In" is often used to denote a space or context, which aligns with the abstract and encompassing nature of "world." For instance, "in the world" implies a broader context or scope, whereas "on" or "at" might suggest a more specific location or point within the world. The use of "with" is less common in this context, as it typically implies a relationship or accompaniment rather than a context or space.

In conclusion, "in" is the preposition of choice before "world" in English due to its alignment with the semantic field of the word and its prevalence in linguistic data. This choice reflects the conventions of English grammar and the way the language is used in everyday communication.