Which word formation process involves creating new words by removing what is mistakenly considered a suffix, typically by deleting the final syllable of the root word?

Explanation

Option D is correct. Backformation is the process where a new word is created by removing an affix that is incorrectly assumed to be part of the original word, usually by dropping the final syllable. The other options describe different word formation methods: compounding (A) joins two words, portmanteau (B) blends parts of words, and derivation (C) adds affixes to roots.