Indispensible
par 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