when

"When" is a word that serves multiple functions in the English language, primarily as an adverb, a conjunction, and a noun. As an adverb, "when" is used to indicate the time at which an action occurs. For example, "I will call you when I arrive." In this context, "when" is a subordinating conjunction that introduces a dependent clause, providing information about the time of the main clause. As a conjunction, "when" can also introduce a dependent clause that provides a reason or cause. For instance, "I will go to the store when I need milk." Here, "when" indicates the condition under which the action will occur. As a noun, "when" refers to a particular time or moment, often used in questions to inquire about the timing of an event. For example, "When will the meeting start?" In this usage, "when" is a noun functioning as the subject of the sentence. The word "when" is derived from the Old English word "hwanne," which has its roots in the Proto-Germanic word "*hwanō." Its usage and meaning have evolved over time, reflecting changes in the English language and its speakers' understanding of time and causality.