以 (yǐ): With / By (Formal) | Chinese (Mandarin) Grammar

以 (yǐ) is the literary sibling of the everyday instrument coverb 用. In Classical Chinese 以 was the all-purpose word for "with / by means of / according to," and in the modern language it survives almost entirely inside fixed frames and written register — announcements, contracts, essays, speeches, and four-character idioms. You will rarely say it out loud in casual conversation; you will read it constantly. Its two highest-value patterns are the workhorse 以…为… ("take / regard X as Y") and manner phrases like 以…的方式 ("in an X manner"). Because 以 is a classical residue, it reads compactly, takes no measure words, and sounds stiff the moment you use it where a native speaker would just say 用. The reframing for English speakers: don't treat 以 as a free everyday preposition — treat it as a formal register signal, and reach for 用 / 拿 when you actually speak.

以 as means and manner: "with / by / in"

The basic frame is 以 + noun + verb, marking the means or the manner of an action. It is productive inside formal noun phrases (以书面形式 "in writing," 以这种方式 "in this way") and inside set four-character sayings (以身作则 "lead by example," 以理服人 "convince with reason").

请以书面形式提交申请。

qǐng yǐ shūmiàn xíngshì tíjiāo shēnqǐng

Please submit your application in writing. (formal) — 以书面形式 = 'in written form', the means of submitting.

作为队长，他总是以身作则。

zuòwéi duìzhǎng, tā zǒngshì yǐ shēn zuò zé

As captain, he always leads by example. (formal, idiom) — literally 'uses his own body as the rule'.

我们应该以理服人，而不是靠权力压人。

wǒmen yīnggāi yǐ lǐ fú rén, ér bú shì kào quánlì yā rén

We should win people over with reason, not overpower them with authority. (formal / literary)

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The quickest register test: if you can swap 用 in and it still sounds natural, you are in spoken Chinese and should use 用, not 以. 'Eat with chopsticks' is 用筷子吃饭 — never 以筷子吃饭. 以 belongs to writing and to set phrases where 用 would sound too plain.

以…为…: take / regard X as Y

This is the single most useful 以 frame and the one worth drilling. 以 A 为 B literally says "take A as B" and translates as "regard A as B / make A into the B." The 为 here is wéi ("to be / to act as"), not wèi ("for") — a tone distinction that also flags the meaning. Several sub-frames are so common they behave like set expressions:

Frame	Meaning	Example
以…为主	with X as the main part	以蔬菜为主 (mostly vegetables)
以…为荣	take pride in X	以祖国为荣 (proud of one's country)
以…为准	take X as the standard	以官网信息为准 (the website info is authoritative)
以…为例	take X as an example	以中国为例 (take China as an example)

大家都以他为榜样。

dàjiā dōu yǐ tā wéi bǎngyàng

Everyone takes him as a role model. (neutral–formal) — 以他为榜样 = regard him as the model.

这家餐厅以川菜为主。

zhè jiā cāntīng yǐ chuāncài wéi zhǔ

This restaurant mainly serves Sichuan cuisine. (neutral) — 以…为主 sets what dominates.

我以你为荣。

wǒ yǐ nǐ wéi róng

I'm proud of you. (formal / heartfelt) — a fixed, elevated way to say 我为你骄傲.

民以食为天。

mín yǐ shí wéi tiān

For ordinary people, food is the most important thing of all — literally 'the people take food as heaven'. (classical proverb)

以便 and 以免: purpose and prevention

Two fused conjunctions built on 以 introduce a following clause. 以便 (yǐbiàn, "so as to / in order to") points at a desired result you want to enable; 以免 (yǐmiǎn, "so as to avoid / lest") points at an unwanted result you want to head off. They are opposite in polarity, and both belong to careful written register.

请留下您的联系方式，以便我们及时通知您。

qǐng liúxià nín de liánxì fāngshì, yǐbiàn wǒmen jíshí tōngzhī nín

Please leave your contact details so that we can notify you promptly. (formal)

请提前预订，以免临时没有座位。

qǐng tíqián yùdìng, yǐmiǎn línshí méiyǒu zuòwèi

Please book ahead, so you're not left without a seat at the last minute. (formal)

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Match the polarity: 以便 takes something helpful (以便联系 'so we can get in touch'), 以免 takes something unwelcome (以免迟到 'so as not to be late'). Swap them and you reverse your meaning — 以便迟到 would literally invite the very thing you want to avoid.

Common Mistakes

1. Using 以 like colloquial 用 in casual speech. 以 sounds bookish in everyday sentences; the spoken instrument coverb is 用.

❌ 我以手机看新闻。

Marked / bookish — in speech the instrument is 用: 我用手机看新闻.

✅ 我用手机看新闻。

wǒ yòng shǒujī kàn xīnwén

I read the news on my phone. (informal) — 用 for everyday means.

2. Dropping 为 in the 以…为… frame. The pattern is a matched pair; 以 alone leaves the sentence hanging.

❌ 我们公司以质量。

Incomplete — the frame needs its partner 为: 以质量为本.

✅ 我们公司以质量为本。

wǒmen gōngsī yǐ zhìliàng wéi běn

Our company puts quality first. (formal) — 以…为本 = take X as the foundation.

3. Swapping 以便 and 以免. They carry opposite polarity; the wrong one flips your intent.

❌ 请戴口罩，以便传染。

Wrong polarity — you want to prevent infection, so use 以免, not 以便.

✅ 请戴口罩，以免传染。

qǐng dài kǒuzhào, yǐmiǎn chuánrǎn

Please wear a mask so as not to spread infection. (formal)

4. Confusing 以为 with 认为. 以为 is a separate verb meaning "assume (mistakenly)" — it implies you turned out to be wrong. For a considered opinion you still hold, use 认为.

❌ 我以为这个方法最好，所以一直在用。

Contradictory — 以为 signals a mistaken belief you've since dropped, clashing with 'still using it'; use 认为 for an opinion you hold.

✅ 我认为这个方法最好。

wǒ rènwéi zhège fāngfǎ zuì hǎo

I think this method is the best. (neutral) — 认为 states a held view; 以为 would mean you were wrong about it.

Key Takeaways

以 (yǐ) is the formal / written coverb for means, manner, and basis — "with / by / according to" — the literary sibling of spoken 用.
Its workhorse frame is 以…为… ("take / regard X as Y"): 以他为榜样, 以…为主, 以…为荣, 以…为准. The 为 is wéi, and it must be present.
以便 enables a good outcome ("so as to"); 以免 prevents a bad one ("lest") — opposite polarity, both written register.
Reserve 以 for writing and set idioms (以身作则, 民以食为天); in speech, swap in 用 / 拿.
Don't confuse the false friend 以为 ("assume, mistakenly") with 认为 ("think, hold as an opinion").

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