indispensable tool

Translations
незаменимый инструмент
The internet has become an indispensable tool for research.
Интернет стал незаменимым инструментом для исследований.
Definitions
An indispensable tool is a necessary and essential instrument or device that is crucial for accomplishing a specific task or function, without which the task would be significantly more difficult or impossible to complete.
Words
indispensable

adjective
незаменимый
tool

noun
инструмент