Find the word that can be formed using the given set of letters: "G", "A", "R", "N", "I", "T".

Let's check each option using the pool of letters $\{\text{G},\text{A},\text{R},\text{N},\text{I},\text{T}\}$:
* "NIGHT": Contains 'H', which is missing.
* "GRIND": Contains 'D', which is missing.
* "TRAIN": Contains 'T', 'R', 'A', 'I', 'N'. All letters are available in the pool.
* "GEAR": Contains 'E', which is missing.