1. So far means [up to now]. It tells what has happened until this moment and might keep going. For example, "So far, I've read five chapters" [means you have read five chapters up to now and might read more later.] 2. Until now: This means [up to this moment.] It tells what has happened until this moment and suggests that it might change now. For example, "Until now, I haven't tried sushi" [means you have not tried sushi before, but you might try it now or soon.] - So far: talks about what has happened up to now and might continue, and - Until now: talks about what has happened up to now and might change.

Es como la diferencia entre 'por ahora' y 'hasta ahora'.

"Until", being a preposition, takes an object. When you say "until X" you turn X into some sort of limit and draw attention to the importance of that limit. Thus "It didn't rain until 4pm" means that 4:00pm was a significant moment that set a limit to the period when "it didn't rain". Likewise, "it didn't rain until now" means that NOW is a significant limit terminating the truth of "it didn't rain". The limit need not be a time limit. "Jack was happy until Jim moved in next door" means Jim moving next door put an end to Jack's happiness. "So far" creates no limits. Also, having no direct object, it calls attention to nothing in particular.

"So far" and "until now" both refer to the time up to the present, but with different nuances: "So far": * Usage: Indicates progress or development up to now. * Example: "So far, everything is going well." "Until now": * Usage: Marks a change happening at the present moment. * Example: "I didn’t know about this until now." Key Difference: * "So far": Ongoing progress. * "Until now": Change or new development starting now.