Many people on here will try to convince you that sex is biological and gender is a social construct. This is not true. Gender and sex are both synonyms for each other. It is impossible for there to be a third gender or more because there are only two chromosome types a baby can have. If a child has a Y chromosome, their sex AND gender is male. If they do not have a Y chromosome, they are female. No matter what gender you believe you are, you are one or the other and it is determined at birth. Gender cannot be changed because you cannot remove the Y chromosome from every cell in the body. Non-binary and trans genders are not actual genders. This does not mean I do not view you as a normal human being, it just means you have a mental illness causing that idea. It IS a mental illness. 'Transgender' people have a suicide rate ranging from 30% to 52%, which is higher than any group of people in the world. This means that if you line up four transgender people, statistically speaking, one or two out of the four will commit suicide. Think about it.
Gender is different from what sex is. Your sex is whether you are born a boy or a girl. Your gender is whether you class yourself as transgender or a boy but in a girl's boy etc.
They are not the same thing. The definition of gender is different to the definition of sex.
According to the Oxford definition, the meaning of the term "gender" "is also used more broadly to denote a range of identities that do not correspond to established ideas of male and female." Therefore, the correct answer in this case is NO. Comments welcome.
I would like to also point out that there's a lack of evidence pertaining to the YES voted thus far.
I would like to point out that in ways, there are more than one sex (assigned at birth) and gender (chosen during life). For one thing, people can be born neither male or female, or even both. They could have the genitalia of both sexes. Sex is also based on the type of chromosome. For example: XX are the chromosomes of biological women, and XY are the chromosomes of biological men; there are still other combinations out there (although rare) that are neither of these, so they are technically neither male or female.
As for gender, it is a matter of opinion. Some disagree and state that you cannot be anything but female or male. I believe you can be other things, such as: gender non-conforming, gender fluid, agender, non-binary, etc., etc.. Gender is decided when a person deems themselves other than the usual female or male, or when a person decides to stick with their assigned sex.
Overall, gender and sex ARE different things, and there are more than one of both. There are several facts regarding this debate, and if a person believes otherwise, so be it. Gender is a matter of opinion, while for sex, it is a matter of facts. Whatever you believe, you should respect the opinion of others.