Complex sentence: The concept of martingale in probability theory was introduced by Paul Lévy in 1934, though he did not name them: the term "martingale" was introduced later by, who also extended the definition to continuous martingales.
Split into simpler sentences: The concept of martingale in probability theory was introduced by Paul Lévy in 1934, though he did not name it. The term "martingale" was introduced later by, who also extended the definition to continuous martingales.