Final answer:
A substantial step in criminal law refers to a preparatory act that indicates the intent to commit a crime, but it is not a completed crime itself. It is a significant action that demonstrates a clear intention to carry out the illegal act.
Step-by-step explanation:
In criminal law, a substantial step refers to a preparatory act that indicates the intent to commit a crime. It is not a completed crime itself, but rather a significant action that demonstrates a clear intention to carry out the illegal act. For example, if someone purchases materials with the intention to build a bomb, that would be considered a substantial step towards the crime of terrorism.