Trends in Ecology and Evolution recently published an article discussing various definitions of gender equality in science, and their respective limitations and pitfalls. This is one of the reasons why working with equality is difficult, because it can be measured along many different dimensions.
You can find the article information here: “What is gender equality in science?”, O´Brien et al. (2019) TREE 34(5):395-399.
If you would like to read the article but do not have access, please email firstname.lastname@example.org. She can provide you with an author-supplied copy.