Judicial relates to courts, judges and the administration of justice — judicial review, the judicial branch. Judicious means showing good judgement — a judicious decision, judicious use of resources. One is institutional, the other a compliment.
The core difference
Both from the same root, but one names a branch of government and the other praises a choice.
- judicial — of courts and judges: judicial independence, a judicial inquiry.
- judicious — sensible, well-judged: a judicious selection.
Why the mix-up matters
"A judicial use of resources" reads as though a court were involved. In writing about government or law the swap is genuinely confusing, because judicial has a precise institutional meaning that judicious does not share.
The third word
Judicatory relates to the administration of justice and is rare. Juridical relates to law and legal proceedings, and is closer to judicial than to judicious — worth knowing if you meet it.