Is Religion Required to Declare Something a Sin?

If you are a religious zealot, this post is not for you. However, if you are a thinker, a philosophy aficionado, or a non-religious person, dive into this thought.

Does declaring something a sin require a religious premise?

In other words, if I were non-religious, could I acknowledge something as sin?

I could most certainly acknowledge something as wrong. I could acknowledge something as immoral. Sin is not necessarily a synonym for either wrong or immoral, despite what Webster's thinks.

Morality can exist without religion or Faith.

Sin carries with it a religious connotation. Let me illustrate how easy the religious implication comes about.

If I were to ask you if homosexuality were a sin, you would be inclined to say No. There is nothing wrong with homosexuality. Ask a religious person the same question.

If you were to ask me if murder were a sin, what would be your response?

I'm leaving this open ended. As a non-religious man, I don't think I could accept either question as valid. If rephrased as whether homosexuality or murder were wrong, then I could answer. Are either sins? That, I cannot entertain as I am not a religious person. Sin does not exist in my world. It might as well not be a word. Do you see what I'm getting at?