John, the best thing you can do is compare the word "acaso" to the English "is it the case" (expressing a certain degree of incredulity)... since it is exactly the same Latin origin of this word and I have heard it in English a few times, though a lot less than the Spanish version. But if you see "¿acaso no tienes tiempo mañana?" it is "is it the case that you don't have time tomorrow?"... it will be a lot easier to understand than the other words you provided before. You have to take into account that common structures in one language maybe rare in other languages, or even in the same language spoken in a different country. Some examples of "acaso" Ella preguntó si acaso estarías mañana She asked if you would be here tomorrow Lit. She asked if it would be the case that you would be here tomorrow ¿Me vas a decir acaso que todo está mal? Are you going to tell me that everything is wrong? Lit. Is it the case that you are going to tell me that everything is wrong? Yo no sé si acaso ella sabe o no I don't know if she know or not Lit. I don't know if it is the case that she knows or not. I hope this is helpful.

"Acaso" can express a doubt , and also a possibility or contingency. " Debemos salir temprano, por si acaso " = We must go out early, just in case (Specify a future hypothesis and indicates its consequences: in case there's much traffic ) " Acaso puedes negar que ese cuadro es hermoso ? " = Is that you can deny that this picture is beautiful ? " Acaso pensabas aprobar el examen sin estudiar ? " = Perhaps did you think to pass the exam without studying ? In this sentence, "acaso" indicates that it assumes certain the opposite of what is said. You can also translate: Really were you thinking to approve the exam without studying? " Por si acaso " = Just in case. If something comes to happen or has happened once. "How do you use" = Cómo usas / Cómo se usa / Cómo lo usas I hope that my explanation was clear, because my english isn't good. Best wishes Sofía.

It´s very simple that word is sarcasm of "quizá" and "tal vez" ( perhaps, maybe) It will never be used with good intention. ¿Vas a ir a cenar con nosotros? Tal vez¿ tu me vas a pagar mi comida? (This would be a normal way to ask) ¿Vas a ir a cenar con nosotros? ¿Acaso tu me vas a pagar mi comida? (This is a very sarcastic way to ask if he/she is going to pay for the food, like if the person doubt it) In english sarcasm is used ALL the time so in english it would be Are you going to pay for my food?

La palabra acaso casi no se utiliza en español,viene a significar por casualidad , tal vez.. Cuando se usa suele ser en oraciones condicionales como: Si acaso vas al supermercado compra fruta If you go to supermarket buy fruit