Why do we use the word ‘lent’ (貸す kasu) when we want to borrow something in Japanese?

The word ‘lent (貸す kasu)’ or ‘borrow (借りる kariru)’ in Japanese are quite clear. But it’s start getting confusing when people suddenly teach you to use ‘lent’ when you want to ‘borrow’ things in Japanese. So let’s clear things up!

FIRST!
貸す（kasu） is ALWAYS to lend
借りる（kariru）is ALWAYS to borrow

Note they are the dictionary form and depending on the conjugation, they can have a lot of different forms.

貸す（kasu)
貸します（kashimasu)
貸さない (kasanai)
貸しません (kashimasen)
貸した (kashita)
貸しました (kashimashita)
貸して (kashite)
貸しまして (kashimashite)

and so on…

借りる（kariru）
借ります (karimasu)
借りない (karinai)
借りません (karimasen)
借りた (karita)
借りました (karimashita)
借りて (karite)
借りまして (karimashite)

and so on…

These are the basic and they are clear as a crystal.

傘を貸しました
kasa o kashimashita
(I)lent the umbrella.

傘を借りました
kasa o karimashita
I borrowed the umbrella.

When you want to borrow something, people will teach you these sentence below and it’s start to get confusing. I want to borrow, but why I use the word “lent” instead? It’s because the natural English translation is different than the literal translation.

English translation for this sentence below would be “May I borrow your umbrella?”. Now check the literal translation below.

傘を貸してもらえませんか？
kasa o kashite moraemasenka?
Could I receive a favor of you lending the umbrella to me?

傘を貸してくれませんか？
kasa o kashite kuremasenka?
Could you give me a favor of lending the umbrella to me?

The literal translations are not natural in English and therefore it’s translated as “May I borrow your umbrella?” which bring a lot of confusions to learner.

The key point of this confusing sentence is in the auxiliary verb くれる (kureru) and もらう (morau). You can learn more about them in this article which explains the different between あげる (ageru), くれる (kureru) and もらう (morau).!

We hope this article helps to clear things up! Happy learning ｡ﾟ✶ฺ.ヽ(*´∀`*)ﾉ.✶ฺﾟ｡