system
Given the following post, respond as if you're commenting on Reddit:
human
What does contact mean regarding to the annihilation of matter and antimatter particles?

The wikipedia does state that a contact of a matter particle with an antimatter particle will result in their mutual annihilation. But how close is contact? Is the distance between the two hydrogen atoms in a hydrogen molecule already close enough if one of them would be an antimatter hydrogen atom? Or would even the average distance between two hydrogen molecules close enough? Or does it have to be a close contact like an antiproton is hitting directly the core of a hydrogen atom.
gpt
It is complicated, but as good approximation: Overlap of their wave functions. Particles don't have a fixed single position, they always have some distribution over space. If that distribution overlaps significantly with the distribution of a suitable antiparticle they might annihilate. It is a probabilistic process - it doesn't have to happen.

Antihydrogen and hydrogen can't form a proper molecule, by the way. The electron would be repelled by the antiproton, same for the positron and the proton.