* Typo: This is the most common term, referring to a simple mistake in typing.
* One-letter word puzzle: This is a general term for any puzzle or game that involves changing one letter in a word to make another.
* Word ladder: This is a type of word puzzle where you change one letter at a time to transform a starting word into a target word.
* Mutation: This is a scientific term that can be used to describe a single-letter change in a gene, but it can also be used more generally to describe any change, including a one-letter word change.
The most appropriate term will depend on the specific situation and the context in which the word change is happening.