sex vs gender?

After reading Lorber's The Social Construction of Gender, I began to realize how often I use the terms 'sex' and 'gender' synonymously without ever giving much thought to their true meanings. Sex can roughly be defined as the biological characteristics that define men and women (penis and vagina) whereas gender is neither biological nor physiological. Gender is a social construct, a cultural phenomenon, it is the word we use to describe stereotypes of masculinity and femininity, and most importantly, gender is a performance. As Lorber states, we all do gender, "[it] is one of the major ways that human beings organize their lives" (122). 'Doing gender' is the way we identify ourselves and others within society. We observe all of the rules that pertain to proper masculine or feminine behavior from a very young age and then learn to assimilate to them as we grow up and interact with society. If I see a stranger walking down the street, I am able to quickly lump them into one of two sex categories just from observing their physical characteristics. We can, for the most part, predict anyone's sex without ever having to look at their sexual organs because physical characteristics are gendered characteristics.