I understand that both Quizá and Acaso are translated to "Perhaps" or "Maybe" in English. Is there any difference between these two words in Spanish, other than quizá being apparently more common? Or are they completely interchangable?
ACASO can mean "in the event that" as in "por si acaso", indicating eventuality.
¿Acaso no lloran las flores? Is it not true (or is it not the case) that...?
In both cases it is used in a subjunctive phrase, indicating possibility.
QUIZÁ indicates "doubt," "possibility," or "potentiality" As in "quizá llueva mañana", equivalent to "tal vez".
It is also used as "maybe".
I cannot explain clearly the difference, but what I can state is that they are not completely interchangable. And there are many examples:
Quizá llueva mañana
Acaso llueva mañana
Quizá lo necesite
Acaso lo necesite
-¿Vendrás a la fiesta?
-¿Vendrás a la fiesta?
In fact, all the previous sentences using 'acaso' sound completely wrong for me...
My suggestion is to translate both 'maybe' and 'perhaps' as: 'quizá', 'quizás' or even 'a lo mejor'.
I use 'acaso' very few times, only in sentences like:
¿Acaso tengo yo la culpa?
Llevaré un abrigo por si acaso hace frío
For me 'acaso' is more paired with 'de casualidad', 'será', among others.
'Acaso' is a word which means some kind of doubt but that I'd only use on interrogative questions like these:
¿Acaso quiere que también lave la ropa?
¿Acaso ese hombre se atreverá a robarme?
and perhaps using certain tone of alarm and concern.
On the other hand, 'quizás' is a word as well used to mean some kind of doubt but more flexible, you can use it on affirmative and negative sentences:
Quizás mañana vayamos al cine.
Quizás la suegra no venga mañana, ¡qué bueno!
Acaso is for defending yourself from something, because someone is blaming on you for something that you didn't do... for example:
-"Debes pagar la ventana" - "¿Acaso yo la rompí?" - "You must pay the window" - "But I didn't break it" or "did I break it?"
And quizá is when you can't make a decision in a situation in which you don't know for sure what will happen or if you're guessing what could possibly happen.. for example..
- ¿Irás a la fiesta? - Quizá vaya. - Will you got to the party? - Maybe I'll go.
- ¿Y que te dirá? - Quizá que quiere romper conmigo. - ¿And what will she say? - Maybe she wants to break up with me.
You can also use acaso when you're going to do something but then you think of something (that you are not prepared for) will happen, for example:
- Si acaso ella te dice algo acerca de la ventana, dile que mañana le llevas el dinero. - Maybe she says something about the window, tell her you'll pay her back tomorrow.
and also when you are forecasting something and you take action against that ...
- Toma esta sombrilla por si acaso llueve.
- Take this umbrella in case it rains.
I'm a native spanish speaker.
My answer will be localized to Mexico. (I don't know if it extends to other areas or not.)
Quizás or quizá mean maybe / perhaps.
Acaso doesn't have a single word equivalent in English. Here are the two common ways of using it:
Llévate un paraguas por si acaso.
This means: Take an umbrella just in case.
¡¿Acaso pasó el camión de basura sin tomar lo nuestro OTRA VEZ?!
Here is a loose equivalent: Did the trash truck really skip our house AGAIN?!
I just checked the entry in Collins. It's a bit more comprehensive than this but definitely in line with my examples, so I'll refer you to it for a more complete treatment.