Collisionless

Collisionless has multiple meanings:

• In information theory and computer science, collisionless refers to computer networking architectures where packets of data cannot collide on the network as is possible in a protocol like ethernet. For example, token ring networks are collisionless.
• Also in computer science, collisionless refers to situations where collisions, or occurrences of the same value, cannot occur in a structure (and prevent reliable lookups). See Hash collision.
• In cosmology and physics, collisionless refers to a medium in which the interaction cross-section between particles is so low that collisions between particles have no significant effect on the system. Examples include dark matter and low-density plasmas subjected to high magnetic fields.