“A hypothesis is a proposed explanation or proposition that can be investigated against evidence.”

What does “proposed” mean?

It means:

put forward for consideration, but not yet established as true.

For example:

“Institutional prestige influences scholarly citation.”

That's a proposition.

You haven't yet established whether it is true.

You can investigate it by examining data.

Explanation versus proposition

These aren't identical.

Proposition

A proposition is a statement that can be true or false.

Example:

“Historians at elite universities receive more citations.”

Explanation

An explanation tells us why something happens.

Example:

“Historians at elite universities receive more citations because institutional prestige increases visibility and network access.”

The first is primarily a claim.

The second proposes a mechanism or reason.

So:

Hypothesis is a testable proposed claim, which may describe a relationship or propose an explanation for it.