Origin: Latin suffix -al
Illegal has 3 different meanings across 1 category:
An illegal act or technique.
"The referee called a foul because the player used an illegal technique to block the opponent from scoring."
"The police arrested two people on charges of illegal trafficking."
Usage: Use "illegal" only as an adjective to describe actions or things that break the law; it should never be used as a noun to refer to the act itself. Instead of saying something like "that's an illegal," say "that's an illegal act."
Contrary to or forbidden by law, especially criminal law.
"The police arrested the man for selling illegal drugs in an alleyway behind the market."
In plain English: Illegal means something that is against the law and not allowed by the government.
"The police stopped him because he was driving with an illegal number plate."
Usage: Use "illegal" to describe actions or things that violate specific laws, such as driving without a license or selling prohibited goods. Avoid using it for moral wrongs that are not technically against the law, like lying to a friend.
The word "illegal" comes from the French illégal, which was borrowed from Medieval Latin and originally meant "not lawful." Its modern usage in contexts like immigration developed later through shortening phrases such as "illegal alien" or "illegal immigrant."