| essential(adjective, characteristic, important, significant, original) |
| necessary(adjective, important, significant, original, essential) |
| vital(adjective, important, significant, original, serious) |
| fundamental(adjective, characteristic, important, significant, natural) |
| basic(adjective, characteristic, important, significant, natural) |
| cardinal(adjective, important, significant, original, essential) |
| critical(adjective, important, original, serious, essential) |
| primary(adjective, important, significant, original, serious) |
| inherent(adjective, characteristic, essential, basic, fundamental) |
| principal(adjective, important, significant, original, serious) |
| underlying(adjective, important, original, essential, basic) |
| basal(adjective, important, significant, original, essential) |
| chief(adjective, important, significant, serious, capital) |
| elemental(adjective, important, significant, original, essential) |
| elementary(adjective, characteristic, important, significant, natural) |
| intrinsic(adjective, characteristic, important, significant, natural) |
| capital(important, essential, vital, earnest) |
| primitive(adjective, important, significant, original, essential) |
| radical(adjective, important, significant, original, essential) |
| substratal(adjective, important, significant, original, essential) |