1Attached to the -masu stem of a verb, expresses that doing something is difficult or awkward — a polite, indirect way of stating inability, often used to decline something formally.
その要求には即答しかねます。
I cannot answer that request immediately.
突然のご依頼ですので、すぐにはお引き受けしかねます。
Since this request is so sudden, I'm afraid I can't accept it right away.
個人的な事情のため、詳しくは申し上げかねます。
For personal reasons, I'm unable to go into the details.
2For one thing to serve two or more roles or functions at the same time — often used in the pattern "serves as both A and B."
彼は社長と最高技術責任者を兼ねている。
He serves as both president and chief technology officer.
この部屋はリビングと寝室を兼ねている。
This room serves as both a living room and a bedroom.
今回の出張は取引先への挨拶と新製品の説明を兼ねていた。
This business trip served both as a courtesy visit to the client and an explanation of the new product.
3For one person to hold multiple jobs or positions at the same time; close in meaning to "to concurrently serve."
彼女は営業部長と広報担当を兼ねている。
She works as both sales manager and PR representative.
小さな会社では、一人が経理と総務を兼ねることも多い。
At small companies, it's common for one person to handle both accounting and general affairs.
4To hesitate to do something, or find it hard to do, out of consideration for someone else's feelings or position.
彼の気持ちを考えると、正直な意見を言いかねる。
Considering his feelings, I find it hard to say what I honestly think.
彼女の立場を思うと、その頼みを断りかねた。
Thinking of her position, I found it hard to refuse the request.
5An older, less common usage meaning to do something with an eye toward the future as well as the present.
記念にもなり、将来の実用にも役立つ品を兼ねて用意した。
I prepared something that would serve as a keepsake as well as be useful in the future.