Final answer:
When I want to ascertain the correct pronunciation of an unfamiliar English word, I check in a reputable dictionary.
Step-by-step explanation:
To ascertain means to find out or learn with certainty, which is the appropriate term for confirming how a word is pronounced. Reputable dictionaries not only provide spellings and definitions but also phonetic guides or even audio clips to help with pronunciation.
When using a dictionary to ensure that you are spelling words correctly and using them in the proper context, you are also increasing your vocabulary, which is beneficial for your overall language proficiency.