“hi” in braille
⠓⠊2 lettersUncontracted
Written letter by letter, hi in braille is h-i, one cell for each letter: ⠓⠊.
Cell by cell
Capitals
Braille letters are lower case unless marked. To start with a capital, as at the start of a sentence, put the capital sign, dot 6, before the first letter: ⠠⠓⠊. For the whole word in capitals, HI, use two capital signs: ⠠⠠⠓⠊.
Grade 1 and Grade 2
This is uncontracted (Grade 1) braille, every letter written out, which is where learners start. Books, signs and labels mostly use Grade 2, where common letter groups and words take a single cell, so some words come out shorter there. See the Grade 2 contractions.
Remember it, don't just look it up
Hi is in Short words. Braille a Day brings it back tomorrow to answer from memory, then again just before you'd forget. Five minutes a day.