3 words in this vocabulary list
verb A word that expresses an action, occurrence, or state of being. In this case, 'classified' is the past tense of the verb 'classify', which means to categorize or arrange things according to a particular system.
adjective A word that describes or modifies a noun or pronoun. In this case, 'classified' is describing something that is kept secret or restricted.
noun a type of aircraft that can fly in both the atmosphere and outer space
noun a type of aircraft that remains aloft by using buoyant gas, such as helium or hot air