This is the 5407th most frequent Russian word.
партнер
Partner.
In this sentence, 'партнер' refers to a business associate or colleague.
Я всегда могу положиться на своего партнера в бизнесе.
I can always rely on my partner in business.
Here, 'партнер' is used to describe a dance partner—a collaborator in a specific activity.
Она мой партнер по танцам в нашей танцевальной группе.
She is my partner in dancing in our dance group.
In this context, 'партнер' indicates someone with whom the speaker collaborates to achieve a shared goal.