| central(adjective, main, private, mental, focus) |
| essential(adjective, important, significant, main, private) |
| main(adjective, important, significant, key, chief) |
| principal(adjective, key, chief, focus, foremost) |
| fundamental(adjective, important, significant, key, main) |
| pivotal(adjective, important, central) |
| vital(adjective, key, chief, foremost) |
| convergent(adjective, convergent) |
| interior(adjective, private, mental, central, inner) |
| important(adjective, focus) |
| inner(adjective, private, mental, central, physically) |
| key(adjective, important, significant, main, chief) |
| middle(adjective, central, centrality) |
| primary(adjective, important, significant, key, main) |
| prime(adjective, important, significant, key, main) |
| chief(adjective, important, significant, key, main) |
| core(adjective, key, chief, central, foremost) |
| approaching(adjective, convergent) |
| asymptotic |
| basic |