No Stupid Questions

Those seas in particular? Because they are bounded by narrow straights.

A gulf has a more specific definition. A sea has a very broad one.

A gulf is mostly enveloped (engulfed) by land, but fairly open to its parent waters relative to its size on one side. Like a reverse peninsula.

A sea can be just about any large, salty, body of water that is between bits of land. They can have very finite bounds such as narrow straights and rivers mouths, more porous bounds like an archipelago, or broadly open to the ocean / other seas between islands or other land masses.

The question for me is “why is the Persian Gulf not a sea, but the Adriatic Sea is not a gulf?”

I guess part of it is that language changes over time, these things got named by different people over the millennia before they were well mapped. Some are translations from other languages, some are political decisions.

"Is Pluto a planet?" problem, I suppose. I doubt that there is a precise, strict definition, so those seas are called that because "it happened this way historically" and there is no real need to change that.

Probably at the time that the name was coined people thought that it’s a area rather than a gulf. Just like Milford Sound is technically a fjord and not a sound

to me “sea” doesn’t mean anything except for “general water region, smaller than an ocean”. I don’t think that there’s anything wrong with considering those three to be “gulfs”, but I think that people don’t usually think of them that way because unless you study the geography carefully, you might not even notice that they actually are connected to the rest of the ocean.

by the way, fun fact: there is actually a sea that isn’t connected to the ocean and why we don’t call it a lake, I really don’t understand. but that’s the Caspian Sea.