What are words similar in spelling but differing in meaning called?

Solution 1:

The only word to describe what you are asking is paronym.

Bear in mind 'wisdom' is a paronym of 'wise' which differs by more than just one character unlike the examples in your question.

There isn't one word to describe exactly what you have asked but hopefully this answer will suit your needs.

As mentioned by John Lawler in the comments under your question the term is rarely used. In fact it's so rare that the spell-checker software on my Google Chrome web browser doesn't recognise it.

See http://oxforddictionaries.com/definition/english/paronym for in-depth details.