‘Female’, when it’s used in a non-clinical or technical context to describe a human woman. Everyone has a slip here or there, right, so, broad stroke take incoming, but, generally speaking, I’ve never met or talked with anyone who reliably refers to women as ‘females’ who actually respects them. It’s a word you’d use to refer to a complete person only if you see them first and foremost as some kind of specimen, and it reaks to me of poor socialization, unhealthy relationship with that sex, or simply low class.