mathematician who in 1872 published his fundamental theorem on groups and
the type of subgroups now named after him.
Sylow was born in Christiania (now Oslo) and studied at the University of Christiania. For 40 years he taught mathematics in a school in Halden. From 1898 he was professor at Christiania.
Sylow collaborated with Sophus Lie, then professor of mathematics at Christiania, on producing an edition of the works of Norwegian mathematician Niels Abel, published 1881; it was followed by Sylow's edition of Abel's letters in 1901.