Basic principle and First rudiment

Basic principle noun - Principles from which other truths can be derived.

First rudiment and basic principle are semantically related. In some cases you can replace phrase "First rudiment" with "Basic principle", this phrases are similar.

First rudiment noun - The elementary stages of any subject (usually plural).

Basic principle and first rudiment are semantically related. You can use "Basic principle" instead a noun phrase "First rudiment".