Question: is atsui an i adjective?
Answer: What is an i adjective? I adjectives are a form of adjective like atsui (熱い), "hot", or akai (赤い), "red" which end in an "i" syllable (い), and can change to negative forms by adding kunai. For example atsukunai, "it's not hot", or akakunai "it's not red".