Recurring revenue is the portion of the revenue that is going to continue in the future. It provides a growing base of revenue on which management can rely while focusing on ways to grow the business.

on which,為什這里要加介詞on？

介詞on 跟rely 有關。由于rely 是不及物動詞，沒辦法直接跟賓語，需要介詞on 做中介，然后才能接賓語。所以，大家常說：rely on sth. ，這個sth. 就是關系代詞which， 它是on 的賓語。這里是介詞用在關系代詞which 之前的一個例子。

“介詞 + 關系代詞”結構 解說：

“介詞 + which” 就是把介詞提到關系代詞which 之前，它是定語從句中容易見到的語言現象，也是一些網友不容易學會的一個語法項目，問題的重點是這個“介詞”較難確定。但它是有規律可循的，有以下幾種狀況，解析如下：

1. “介詞+ which”可以替代關系副詞when, where, why

替代when

Ill never forget the day on which my son was born.

我永遠忘不了我兒子生的那一天。（on依據on the day確定）

The year in which the earthquake happened was 2008.

發生地震的那年是2008年。（in依據in the year確定）

替代where

This is the office in which I used to work.這就是我過去工作過的辦公室。（in依據in the office確定）

He forgot the exact place in which he had hidden the jewelry.

他忘記了埋藏珠寶的確切地址。（in依據in the place確定）

替代why

Id like you to explain the reason for which you refused my offer.

我想叫你講解一下你拒絕我的幫忙是什么原因。（for依據for the reason確定）

2. 依據與先行詞搭配的具體意義確定用什么介詞

Ill never forget the time during which I was with my friends in the country.

我從來不會忘記和朋友們一塊在鄉村度過的時光。

I will offer you a better way in which you can do the job.

我要給你提供一個做這項工作較好的方法。

3. 依據定語從句中動詞或形容詞的搭配來確定介詞

She bought several clothes, on which she spent all her money.

她買了幾件衣服，這類衣服花光了她所有些錢。（on依據spend…on確定）

It is the grammar rules of which I am not sure.

我沒把握的就是語法規則。（of依據be sure of確定）

4. 依據定語從句所表達的具體意思來確定介詞

Can you see the river across which there is a bridge?

你能看見上面有座橋的那條河？

He is swimming in the river, on which there is a boat.

他在那條河里游泳，河面上有一只小船。

Here is the river in which I used to swim.

這兒就是我過去常在里面游泳的那條河。

【注意】

有的“動詞+介詞”短語被視為一個固定的詞組，不可分割。這個時候不可以把介詞置于關系代詞前，如：listen to, look at, look for, look after, care for, hear from, send for,等。

This is the right book for which Im looking.

This is the right book that Im looking for.

這就是我要找的書。

除此之外，除去“介詞 + which”以外，假如定語從句的先行詞是“人”，那樣也可以用“介詞+whom”引導定語從句，比如：Mary is the girl for whom I bought this gift. 瑪麗就是那個我為其買此禮物的女生。