What is the difference between a malapropism and a spoonerism?

Malapropisms and spoonerisms are both humorous linguistic errors and literary devices. However, there is a key difference:

• Malapropisms confuse similar-sounding words.
• Spoonerisms mix up the initial sounds of multiple words within a phrase.

For example, “You have tasted two whole worms” (meaning “You have wasted two whole terms”) is a classic spoonerism from a 1911 issue of The Strand Magazine.