parallel

Parallel describes a relation between two geometric objects, such as lines or planes, that do not meet within a given geometry and that remain the same distance apart. In the Euclidean plane, two lines are parallel if they lie in the same plane and never intersect; this implies a constant separation and the same direction. The concept extends to three-dimensional space for lines and planes as well, and is a fundamental idea in geometry and design.

In electrical and electronic contexts, components connected in parallel share the same two nodes. The total resistance of parallel components is less than any individual resistance, and currents divide among the branches in proportion to their conductances. Parallel arrangements contrast with series arrangements, where components carry the same current and voltages add.

In computing, parallel processing uses multiple processors or cores to perform tasks simultaneously. Data parallelism applies the same operation to many data items, such as vector or matrix operations, while task parallelism runs different tasks concurrently. Hardware support includes multi-core CPUs, symmetric multiprocessing systems, and graphics processing units. Achieving efficient parallelism depends on minimizing dependencies and communication between tasks; theoretical limits are described by models such as Amdahl’s law.

The term parallel is also used more generally to denote similarity, alignment, or correspondence between things, such as parallels between ideas, events, or trajectories in different domains.

In science and popular culture, the idea of parallel universes or parallel worlds refers to hypothetical or speculative realities that may coexist with our own. While debated in physics and philosophy, the concept is common in fiction and theoretical discussions about cosmology.