essential part

That’s because it’s not true that you can mix every color you can perceive — the very act of mixing reduces a component color’s chroma, or degree of vividness, which is an essential part of that particular color.

This won't help you get tickets, but is an essential part of the annual routine.

In a statement, it told the BBC it targets military sites in accordance with strict protocol, adding that it is "aware of the existence of sensitive sites and this is taken into account and constitutes an essential part of the planning of strikes".

It is a long way from a Chinese endorsement of his disastrous handling of the post-coup chaos in Myanmar, but it does suggest that Beijing sees him as an essential part of a solution to the conflict there.

"Civil rights work and political involvement was no longer an activity to do on the side. It became an essential part of life and humanity."