1. A streakline is the path that a particle will follow in the flow, the locus of particles that have passed sequentially through a prescribed path in the flow. Particles are continuously introduced at a certain point, the streakline shows the line formed due to the release of these particles from the specific point.

2. A pathline is the path that is followed by a particle released into the fluid; the actual path traversed by a given fluid particle. A pathline represents a particle's path.

3. A timeline is lines that represent the same set of fluid particles but which show their position at different moments in time. If one point was taken on a timeline and traced with time, a pathline would be obtained.

4. Some examples…….

5. A streamline is a line that is everywhere tangent to the instantaneous local velocity vector. A streamline represents a velocity path.