A substance capable of donating an electron pair
A compound which can act as an electron pair donor.
a molecular entity (and the corresponding chemical species) that is able to provide a pair of electrons and thus capable of co-ordination to a Lewis acid, thereby producing a Lewis adduct
a molecule which can donate an electron pair to a Lewis acid to form a covalent bond
a species which donates an electron pair to form such a bond
Any species that can make available a share in an electron pair.
A Lewis base is any molecule or ion that can form a new coordinate covalent bond, by donating a pair of electrons, named after the American chemist Gilbert Lewis. The term base is ambiguous. This is one interpretation.