Verb

How do you say “Lose” in Japanese?「失う(うしなう)」Ushinau/「無くす(なくす)」Nakusu

"Lose" is「失う(うしなう)」or「無くす(なくす)」in Japanese. 「(私は)あなたを失うなんて考えられません。」means "I can't imagine losing you."「菅野さんは池にスマホを落として無くした。」means "Kanno-san dropped his smartphone in the pond and lost it."
Verb

How do you say “Decline” in Japanese?「断る(ことわる)」Kotowaru

"Decline" is「断る(ことわる)」in Japanese. 「(私は)飲み会の誘いを断る。」means "I’ll reject the invitation to the drinking party."「申し訳ないですがお断りします。」means "I'm sorry, but I have to decline."
Noun

How do you say “Air” in Japanese? 「空気(くうき)」Kūki

“Air” is「空気(くうき)」in Japanese. 「田舎の空気はきれいだ。」means "The air in the countryside is clean. "「自転車のタイヤに空気を入れます。」means "I’ll pump air into my bike tires."
Verb

How do you say “Be happy” in Japanese?「喜ぶ(よろこぶ)」Yorokobu

"Be happy" is「喜ぶ(よろこぶ)」in Japanese. 「私の結婚式は両親が喜んでくれた。」means "My parents were happy with my wedding."「クリスマスプレゼントを貰って息子は凄く喜んだ。」means "My son was very happy to receive a Christmas present."
Noun

How do you say “Feeling” in Japanese? 「気持ち(きもち)」Kimochi

“Feeling” is「気持ち(きもち)」in Japanese. 「彼の気持ちを聞いて(私は)嬉しくなった。」means "I was happy to hear his feelings."「晴れた朝は気持ちがいい。」means "It feels good on a sunny morning."
Noun

How do you say “Shellfish” in Japanese? 「貝(かい)」Kai

“Shellfish” is「貝(かい)」in Japanese. 「私は魚介類の中でも貝が大好きです。」means "I love shellfish among seafood."「女の子が綺麗な貝を見つけました。」means "The girl found a beautiful shellfish."