| constitutive(adjective, important, essential, critical, basic) |
| decisive(adjective, important, essential, critical, basic) |
| exigent |
| focal |
| heavy(adjective, important, significant, essential, critical) |
| high-priority |
| integral(adjective, important, essential, critical, basic) |
| key(adjective, important, essential, critical, basic) |
| life or death(expression, adjective, idiom, critical, basic) |
| material |
| meaningful(adjective, important, significant, essential, critical) |
| meat-and-potatoes(adjective, important, significant, essential, critical) |
| name(adjective, important, significant, essential, critical) |
| name-of-the-game(adjective, important, significant, essential, critical) |
| needed(adjective, important, essential, critical, basic) |
| nitty-gritty(adjective, important, essential, critical, basic) |
| pivotal |
| prerequisite(adjective, important, essential, critical, basic) |
| required(adjective, important, essential, critical, basic) |
| requisite(adjective, important, essential, critical, basic) |