- A pair.
- In chemistry, a bivalent element, molecule, or ion.
- Two people in an interactional situation, patient and therapist, husband and wife.
- The double chromosome resulting from division in meiosis.
- Two units treated as one.
- A pair of cells resulting from the first meitotic division.
- The transverse tubule and a terminal cisterna in cardiac muscle cells.
[G. dyas, the number two, duality]