A trajectory is the path a moving object follows through space as a function of time.
In control theory a trajectory is a time-ordered set of states of a dynamical system (see e.g. Poincaré map). In discrete mathematics, a trajectory is a sequence (f^k(x))_{k \in \mathbb{N}} of values calculated by the iterated application of a mapping f to an element x of its source.
The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass. A trajectory can be described mathematically either by the geometry of the path, or as the position of the object over time.
Someone who started off on one instrument but changed to another and no longer plays their old instrument and no longer belongs in that section hence transectional. Used commonly among the Sax family and Brass Family