From Latin 'in-' + 'struere' (to build) — building knowledge into a person, equipping the mind.
To teach someone a subject or skill; to direct or command someone to do something.
From Latin 'instruere' (to build in, to arrange within, to set up, to equip, to furnish, to teach), composed of 'in-' (in, into, upon) + 'struere' (to pile up, to build, to arrange layers), from PIE *strew- (to spread, to strew). The root *strew- yields a rich family: 'structure' (what is built), 'construct' (build together), 'destroy' (un-build), 'obstruct' (build in the way of), 'industry' (building within oneself), and the English verb 'strew' (to scatter) itself. The core metaphor of 'instruct' is the furnishing of an empty space: to instruct is to build knowledge into a mind, as one equips a workshop with
The connection between 'instruct' and 'instrument' is direct: both come from Latin 'instruere' (to build in, equip). An 'instrument' was originally any tool used to equip or prepare — something 'built into' a process. A musical instrument, a surgical instrument, and a legal instrument (a formal document) are all 'equipment' in the Latin sense — things