Dear Miss Manners: I am a young man in my 20s, and I am attending university and working as a teaching assistant while I get my master's degree.

I am very small-framed and soft-spoken, and appearance-wise, I look to be about 16. As a result, when I am on campus or in an adult-dominated environment, I am often mistaken for a woman, even though I dress and behave like a fairly typical man.

When students and classmates refer to me as a woman, and I inform them that I am a man, I am sometimes met with, "I know someone who has gone through the sex-change surgery, too." Or they ask me, "Are you having surgery to construct a penis?"

My friends have told me to respond with "It's none of your business," but I feel like this implies that I am in fact having a surgery to change sex, and it would stir rumors.

I completely accept people who do undergo sex reassignment, but I believe it is rude for others to make assumptions about another person's circumstances.

Some friends encourage me to be hostile. I do not want to be hostile to my students, and I know that they are just trying to be open-minded and supportive. How can I politely, but firmly, respond to questions and assumptions like these?

Being the instructor has some advantages, one of them being the ability to instruct others without being thought rude.

Your assumption that they mean well is gracious and perhaps correct. But if those trying to advance the cause of gender tolerance can agree on nothing else, they generally acknowledge that one of the things they are fighting to overcome is people making incorrect and unwelcome assumptions.

“If you are interested in the gender identity question,” you can answer, “this is a really good lesson. I was born, and live as, male. It is dangerous to make an incorrect assumption based on appearance.”

This may change their behavior in the future. And it will give you a brief respite while they absorb the news, which, if you do not want a longer conversation on the subject, is a good time to slip away.

Dear Miss Manners: In the past few years, I have received invitations to various events stating the dress should be "California casual," "European casual" or my personal favorite, "smart casual"!

Judging from the wide variations in the way that people have dressed at these events, I am guessing that I am not alone in my confusion. Would you be so kind as to define these terms?

Your hosts would probably say the word or words added to a more-or-less well-understood term are there to inspire your imagination. What they probably mean is that there should be a conversation starter to justify your choice.

Miss Manners thinks they are a waste of time and ink. Casual is casual. Consider yourself fortunate that none of your hosts’ additions are contradictory, as in “business casual.” Although she would not recommend issuing it as an instruction, she has seen ensembles that can only be described — and not in a complimentary way — as “casual formal.”

New Miss Manners columns are posted Monday through Saturday on washingtonpost.com/advice. You can send questions to Miss Manners at her website, missmanners.com.

2019, by Judith Martin