The IoT-lingo can be very confusing: devices are sometimes called sensor, even if there isn't a single sensing function inside, or if it is fact an actuator. While sensors and actuators by definition both are devices, devices on the other hand need not be sensors or actuators.

 

To set things straight, we've taken the liberty of looking it up in a dictionary for you (source: Merriam-Webster's Online Dictionary):

 

Actuator

noun | ac·tu·a·tor |ˈak-chə-ˌwā-tər, -shə-

a device for moving or controlling something.

Device

noun | de·vice |  \di-ˈvīs\

an object, machine, or piece of equipment that has been made for some special purpose

 

Sensor

noun | sen·sor  | ˈsen-ˌsȯr, ˈsen(t)-sər

a device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control)