- fundamental, rudimentary, underlying - being or involving basic facts or principles; "the fundamental laws of the universe"; "a fundamental incompatibility between them"; "these rudimentary truths"; "underlying principles"
Antonyms: incidental, incident (indirect, via basic)
- rudimentary - being in the earliest stages of development; "rudimentary plans"
Antonym: complete (indirect, via incomplete)
- vestigial, rudimentary - not fully developed in mature animals; "rudimentary wings"
Antonym: developed (indirect, via undeveloped)