Semiconductors are the basic material for the formation of "semiconductor devices".
Examples of semiconductors in electronics are diodes and transistors, but ICs also depend on semiconductors. Another example is the photodiode, which would not be possible without semiconductor technology.
These semiconductors enabled "modern" electronics to emerge and take on many tasks.
The best way to define a semiconductor is by name.
The semiconductor is not a conductive component, but it is also not a real insulator. The semiconductor is defined by two elements, the conductor and the non-conductor.

Depending on the temperature, current, material and voltage, the semiconductor may or may not conduct.
Definition of the semiconductor using the specific resistance
By definition, the resistivity of the semiconductor is also an indication of its purpose and properties, because the resistance is the average of a conductor and that of a non-conductor.
The figure above shows very clearly that the semiconductor stands between the insulator and the conductor.
External influences change the conductivity of the semiconductor. This circumstance is used in electronics in modern circuit technology.