# Words used to describe simulation speed and time

- Real time is actual time, reflected by your computer's operation. This is time outside the software.
- Simulation time is local to the simulated environment and is shared by all scenes in a model. This is time inside the software.
- A tick indicates when quantities or values in a model are updated. For example, simulated quantities such as temperature, mass or pH voltage or current variable value or position may be ticked (updated) 20 times a second.
- Tick period is the real time interval between ticks.
- Time step is the simulation time interval between ticks. This value can be altered.
- You can alter the simulation speed using a slider on the toolbar. Simulation speed can be defined as Time step / Tick period or as Simulation time / Real time.

## See also:

- Using models