The words ‘sex’ and ‘gender’ each have several different meanings, but they are also often used interchangeably to mean ‘the state of being male or female’. However, there is a subtle — and some say important — difference between them when used in this context.
‘Sex’ tends to be used in reference to biological and physiological differences. For example, it could be appropriate to say: ‘A person’s sex will usually determine the presence of facial hair.’
On the other hand, ‘gender’ usually refers to behavioural, psychological, social or cultural differences. So we could say, for example, ‘In that country, gender has a significant impact on salary earning potential.’
The usage of the two terms becomes a little more complicated when you consider that not all biological differences are clear-cut. Many men have feminine physical features, and many women have physical characteristics we associate with masculinity. Furthermore, some behavioural or psychological traits have their origins in biological factors, which might mean that the above distinction between ‘sex’ and ‘gender’ doesn’t help. But that gets us into the nature versus nurture debate, which is beyond the scope of this blog.
For most purposes, however, if you simply remember the ‘sex/biology’ and ‘gender/sociology’ pairings, you shouldn’t go far wrong.