What is the better way to translate "voy a comer pescado manana" in English: "Tomorrow I will eat fish" or "Tomorrow I am going to eat fish"? Duolingo says both ways are correct but I wonder whether there are any subtle differences, e.g. whether the action in phrasal future is a planned one, spontaneous one or it may be both? Thanks in advance!
Just as you show two ways to say it in English, there are two ways to speak in the future tense in Spanish as well. There is the ir form (I am going to...) and then there is the true future tense (I will....), such as comeré. Typically, the ir form is used when you are talking about the near future and the true form when talking of the distant future or habitual actions. An example: En la noche, voy a cenar. En dos años viajaré a Chile. Tonight I am going to eat dinner. In two years I will travel to Chile.
In English the distinction between going to vs the formal future tense often has to do with whether something is your existing plan in which case you use going to vs. if you have just decided something or been talked into something by someone else. Example:
I'm going to Chicago tomorrow. (this is my plan)
Different situation, forget about the above statement, new story:
Boss: somebody needs to go to Chicago tomorrow.
Employee: I'll do it. I'll go to Chicago tomorrow.
Unless the employee was already planning on going to Chicago tomorrow, he would not say "I'm going to Chicago tomorrow"
Later on, that same employee talking to someone else.
Hey buddy, what are you doing tomorrow.
I'm going to Chicago, the boss asked me to.
(Now it's his plan)