Adilen Red-Spider-Man
Adilen Red-Spider-Man voted up Will Holmes' answer

The root of the word 'painless' is 'pain'.

The way to determine root words is to try and remove any prefixes (letters added to the start of a word) or suffixes (letters added to the end of a word), from your chosen word. In this instance, removing the suffix '-less', leaves you with the root word, … Read more