tetrapolar

Tetrapolar means having four poles, typically arranged as two opposite pairs. The term is used in several fields to denote a four-contact or four-pole configuration, where a pole can refer to magnetic or electrical poles, electrode contacts, or genetic loci in biology.

In basidiomycete fungi, tetrapolar refers to a mating system controlled by two unlinked genetic loci, often called A and B, each with multiple alleles. Two individuals are compatible only if they differ at both loci. This arrangement creates many mating types and promotes outcrossing; some species are tetrapolar, whereas others are bipolar, with mating compatibility determined by a single locus.

In electrical measurements, tetrapolar electrode configurations use four electrodes in a line or array. Current is injected through the outer two electrodes, while potential is measured between the inner two. This reduces contact resistance effects and improves accuracy in electrical resistivity surveys, material testing, and bioelectrical impedance analysis (tetrapolar impedance analysis).

The term also appears in instrumentation to describe four-pole sensors or connectors that separate excitation and measurement paths for improved signal integrity.