rudiment

A fundamental principle or skill, especially in a field of learning.

We'll be learning the rudiments of thermodynamics next week.

This boy is forest-born, / And hath been tutored in the rudiments / Of many desperate studies.

A form that lacks full or complex development.

I have the rudiments of an escape plan.

But I will bring thee where thou soon shalt quit / Those rudiments, and see before thine eyes / The monarchies of the earth.

A body part that no longer has a function

In percussion, one of a selection of basic drum patterns learned as an exercise.

Show me your rudiments.

To ground; to settle in first principles.