1. To tell someone to do something; especially, officially or as an employer: "The captain instructed the soldiers to retreat."
2. To teach someone a subject or skill by providing with knowledge; especially, in a methodical way: "A private tutor instructed the brother and sister so they could qualify for the university."
3. To arrange for a lawyer to speak in court or to ask or to authorize a lawyer to act on one's behalf and to supply him or her with relevant information.
4. To give information as a judge to a jury at the end of a case in order to explain the applicable points of law and to summarize what has to be proven.
5. Etymology: from Latin instruct-, the past participle of instruere, "to prepare, to equip"; from struere, "to build".