“Since” can function both as a time adverb and as a subordinating conjunction indicating cause or reason. When used to show time, “since” refers to the point in time from which an action or event started. For example, “I have been studying since yesterday” indicates the starting time of the studying.

On the other hand, when “since” is used to show causality, it introduces a reason or cause for the action in the main clause. For instance, “Since the event occurred, she has been feeling unsettled” implies that the occurrence of the event is the reason she feels unsettled.

The role of “since” in indicating time or causality is determined by the context of the sentence. In time-related usage, “since” typically appears at the beginning of a sentence or clause, followed by the specific time reference. However, in causal contexts, “since” often precedes the cause or reason for the action.

Therefore, the meaning of “since” changes based on whether it is used to denote time or causality, as well as its placement within the sentence. The context surrounding “since” helps to clarify its intended meaning, whether it signifies a temporal relationship or a causal connection.