Indispensible
von Melissa Cheung
1. vital
2. primary
3. Central
4. Key
5. crucial
5.1. Crux
6. essential
6.1. critical
6.2. basic
6.3. foundation
6.4. groundwork
6.5. heart
6.5.1. core
6.5.1.1. connected
6.5.1.2. linked
6.5.1.3. coherent
6.5.2. center
6.5.3. focus
6.5.4. origin
6.5.5. energy