rudiment

Short definition from Wiktionary

Noun

1. 1
   A fundamental principle or skill, especially in a field of learning.
2. 2
   A form that lacks full or complex development.
3. 3
   A body part that no longer has a function
4. 4
   In percussion, one of a selection of basic drum patterns learned as an exercise.

Verb

1. 1
   To ground; to settle in first principles.