I'm writing my research proposal and I have the following sentence:
The excess charge is considered crucial for the membrane penetration process.
I find the word crucial too strong and I'm searching for another word which is less strong in that context. I thought about required but it doesn't "fit well" with the sentence. Can you think about better word?
Also, I remember that there was a website for synonyms which also had some similar meaning words, but I can't find it. Do you know any of that kind?