Practical switch

In electronics engineering, practical switch is the term to describe the condition for a switch that:

has finite resistance during its OFF state
has limited blocking voltage during its OFF state
has limited conduction current during its ON state
has limited switching speed, which consists of rise time and fall time
has switching losses (during switching transition) and conduction losses (during ON or OFF states)
has voltage drop across the switch during its ON state

In contrast to practical switch, the ideal case for switches is called ideal switch.