美味し

In a sentence

• このりんごはとても美味しいです。

  This apple is very delicious.

  Here, 美味しい (oishii) is used as an adjective to describe the taste of the apple.

• 美味しさを求めて、新しいレストランを探しています。

  I'm looking for a new restaurant in search of deliciousness.

  Here, 美味し (oishi) is combined with the noun-forming suffix 〜さ (-sa) to form 美味しさ, which means 'deliciousness' or 'taste quality'.

• 美味しく料理を作るには、新鮮な材料が必要です。

  To cook food deliciously, fresh ingredients are needed.

  Here, 美味し (oishi) takes the adverbial form 美味しく (oishiku) to describe the manner in which the cooking is done.