Correct spelling


Correct spelling, explanation: hitting is created the same way as other verbs made out of short base words ending in a consonant, which means that the ending consonant is doubled to make the word more readable. Take for example to sit or to rob. Sitting and robbing are pretty clear where they come from, but siting and robing point more to a site and a robe than to the verbs. The double consonant is added to specify there is no ending vowel, which is the same with hitting, as the base word is hit not hite.

Definition of hitting:
Adjective, verb
1. The act of punching or striking something or someone with an object or a hand or fist
I shattered my bedroom window by hitting it with a ball.
I’m scared of the thought of an asteroid hitting the Earth.

Incorrect spelling


Incorrect spelling, explanation: hiting is a word that seems plausible and it would be if the base word – to hit – had a vowel at the end (like hite). In these cases, the ending letter is not added when adding an -ing suffix. Otherwise, the letter needs to be added as it points the reader at what the base word was so the word is understandable, so because the base word here is hit, the correct form must be hitting.