What does the word formidable in the passage mean?

Match the definition to the term. 1. pronouns or verbs used to show the person speaking, the person spoken to person 2. a form of noun, pronoun, or adjective used to show its relation to other words gender 3. the grouping of nouns into the classes masculine, feminine, and neuter case 4. an inflection or word form that shows whether one or more than one is meant number 5. pronouns that show by their form personal pronouns