What is the difference between ahi and alli???
Is one more formal than the other?
Actually, "allí" is incorrect, people tends to confuse this due the way some people pronunce the word "ahí". Remember in Spanish "h" doesn't have any sound, only when is after a "c". Due this, the right pronunciation for "ahí" is just "aí " with the right accent at the end. . If you want to say "over there" then you use " allá ", here, the double "L" sounds like "G" in the name Giovanni,
Actually, allí is correct, according to three of my text books and also in Merriam-Websters Spanish English Dictionary.
Both ahí and allí have accents.
Ahí refers to 'there', (probably fairly close by, but you can't reach it). Allí refers to 'over there', even further away than ahí.