When I was a child, pretty much every children's magazine I subscribed to used to publish those little word-chain games where you had to get from one word to another — often an antonym — by replacing one letter at a time. To simplify (or complicate) things a little, you were allowed to take only a certain number of steps. So, for example, you had to build a word chain from "cold" to "warm":

c o l d
_ _ _ _
_ _ _ _
_ _ _ _
w a r m

and one possible solution would be:

c o l d
c o r d
w o r d
w a r d
w a r m

Now, I have two questions:

• What is the English term for a word that differs from another word by just a single letter, the length of both words being the same?
• What is the term for such a word if the length doesn't matter? (Say, "band"-"brand", or "warm"-"war".)

In Russian, the answer to the first question is "метаграмма", which I would translate, or rather transliterate, as "metagramm(e)" (obviously, of Greek origin). However, searching Wikipedia — or, in fact, the entire Web — for the term "metagramm(e)" doesn't seem to return any meaningful results.

As to the second question, I can't answer it in any language I am familiar with.

Can anyone offer any hints?