1. Linear combination of atomic orbitals on an atom. Hybrid orbitals are often used in organic chemistry to describe the bonding molecules containing tetrahedral (), trigonal () and digonal () atoms.
   Source:
   PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1122
2. The formation of stable duplexes of two DNA and/or RNA (complementary) strands via Watson-Crick base pairing used for locating or identifying nucleotide sequences and to establish the effective transfer of nucleic acid material to a new host.
3. The formation of a novel diploid organism either by sexual processes or by protoplast fusion.