Which side of the bed is the left side? Is the answer based on the perspective of laying in the bed (person's head at the head end)? Is the answer based on viewing it from the foot of the bed, looking at the head of the bed? Is there an "anatomical position" or special terminology like in boating for this?
For context:
My boyfriend and I can't agree on this. We change who gets which side based on the shoulder we'd predominantly sleep on and how it's feeling. This let's us get good cuddles before shoulder pain gets irritated. He comes to bed after me. A while back he asked what side I'm sleeping on. I said "left". Later that night, he comes in and almost lays directly on me because he claims "left" is the other side. Since then we have to describe which side using complicated descriptions.
This is the correct answer. It's how ships avoid running into each other. When whoever is steering the vessel is facing the bow (front, usually the pointy bit), port is their left, starboard their right. Ship's running lights are red on the port side, green on the left. So if you're out on the water at night, you can immediately see whether a ship is coming towards you or moving away. The rule for passing an oncoming vessel is "port to port", thus avoiding confusion and collision.
Sitting up in bed I would consider the headboard the stern, because I have my back to it, and the foot the bow. So the area to starboard is right, and portside is left. Ahoy maties!!!
the bed was designed for sleeping. just because you can face any direction while fucking on it doesn't mean anything, because the same can be said of a ship
The majority of people occupying the same bed will have congruent driver/passenger sides. Distant strangers don't need to know which side you are referring to. Couples from different regions could adopt the local convention.