- In chemistry, this refers to an acid and a base which can convert to each other by the gain or loss of a proton (a hydrogen nucleus), which together are called a "conjugate acid-base pair." It can also refer to two liquids in equilibrium with each other.
- In mycology (the study of fungi), this refers to a dikaryon with two haploid nuclei in it.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.