The question of which side of the armrest is really yours at a movie theater can be a subject of debate and can vary depending on the context and social norms. However, there are a few general guidelines that can help determine ownership of the armrest.

1. The unwritten rule of "first come, first served": In most cases, the person who arrives and occupies the seat first is typically given the right to claim the armrest. This principle is based on the understanding that the first occupant has established their territory and should be entitled to the armrest.

For example, if you arrive at the theater and sit down, placing your arm on the armrest, it is generally expected that the person who arrives later should yield to your claim. This principle is often followed in various social settings, including movie theaters.

2. Sharing and compromise: In situations where both individuals arrive at the same time or nearly simultaneously, it may be appropriate to share the armrest. This can involve both parties finding a comfortable position for their arms or even taking turns using the armrest throughout the movie.

For instance, if two people sit down at the same time and both place their arms on the armrest, it would be courteous for both individuals to adjust their positions slightly to accommodate each other.

3. Context and seating arrangement: The layout of the theater and the specific seats can also influence armrest ownership. Some theaters have wider armrests that can comfortably accommodate both individuals, while others may have narrower armrests that make sharing more challenging.

Additionally, if there is an empty seat between two individuals, it is generally accepted that each person can claim their respective armrests without any conflict.

It's important to note that these guidelines are not universally agreed upon or enforced, and individual preferences and cultural norms may vary. In some cases, people may simply avoid using the armrest altogether to prevent any potential conflict.

Ultimately, the best approach is to be considerate and respectful of others' personal space. If a disagreement arises, it is advisable to communicate politely and find a compromise that ensures everyone's comfort.

While there may not be any specific references or official rules regarding armrest ownership in movie theaters, these guidelines are based on common social etiquette and observations of general behavior in public settings.