What does meanwhile modify at the beginning of a sentence?

"Meanwhile" at the beginning of a sentence usually modifies the entire clause that follows it. It indicates that the action or situation described in the following clause is happening simultaneously or concurrently with something else that was previously mentioned.

Think of it as a signal that the story is shifting to a different aspect of the same overall situation, happening at the same time.

Here are some examples:

* Meanwhile, the firefighters were battling the blaze. (This implies the fire is happening at the same time as something else previously mentioned.)

* Meanwhile, the children were playing in the backyard. (This suggests the children are playing while something else is occurring.)

Essentially, "meanwhile" acts as a transition word, connecting two distinct events or situations that are happening at the same time.