ANSWER:
The words energy, athlete and poet are nouns and adding the affix –etic to change the words from its noun form to adjectives, thus change its meanings.
Step-by-step explanation:
Energy is an abstract noun and it expresses the concept. Energetic is an adjective that describes the quality of noun in a sentence. An athlete is a common noun that denotes a person who excels in sport whereas athletic is an adjective that denotes if a person or noun is physically strong or active to excel in a sport. Poet is a common noun. It denotes a person who writes poems whereas poetic is an adjective that relates poetry.