Final answer:
A combining vowel is inserted between word roots even when the second root begins with a consonant to aid in word formation and pronunciation.
Step-by-step explanation:
Most often, a combining vowel is inserted between word roots even when the second root begins with a consonant.
The purpose of a combining vowel is to help with pronunciation and to aid in word formation. It is used to connect two word roots to form compound words or to add prefixes or suffixes to word roots.
For example, in the word 'preheat', the combining vowel 'e' is inserted between the word roots 'pre-' (meaning before) and 'heat' (meaning to make hot) to form the compound word 'preheat' (meaning to heat before).'