in ‧ di ‧ spen ‧ sa ‧ ble /ˌɪndɪˈspensəb ə l◂/ BrE AmE adjective
someone or something that is indispensable is so important or useful that it is impossible to manage without them SYN essential
indispensable to
This book is indispensable to anyone interested in space exploration.
indispensable for/in (doing) something
Meat is not indispensable for maintaining a healthy diet.
Mobile phones have become an indispensable part of our lives.