This is the 3005th most frequent Japanese word.
パートナー
Partner.
Here, 'パートナー' is used to refer to a collaborator or associate in a business context.
私はビジネスのパートナーと新しいプロジェクトを始める予定です。
I plan to start a new project with my business partner.
In this sentence, 'パートナー' is used to describe someone in a personal or close relational role, possibly a life partner or significant other.
彼女は私にとって一番のパートナーです。
She is the best partner for me.
This usage of 'パートナー' specifies a companion in a recreational or activity-oriented context, such as dancing.