Precursory tremors are often associated with slow slip along a plate boundary. Studies have identified four major eruption phases, and one minor precursory tephra fall. From direct observation of precursory signs, it is possible to anticipate eruptions. These precursory signals are intermittent and seem not to occur systematically before every major earthquake. Thus ecotypes and morphs can be thought of as precursory steps of potential speciation. He is said to be precursory to the reform of pedagogy. Definition of the precursory mission and discussions on launch opportunities are currently under way. The precursory mission launch date is yet to be determined. Differences also exist between the precursory pilot and the official series as a whole. As of 2016, neither the launch vehicle nor precursory launch date have been set. This equivalence-value was a precursory formulation of entropy.