only, single, sole, unique, alone

形容詞 only:

1. being the only one; single and isolated from others
   同義詞：lone, lonesome, sole, solitary
2. exclusive of anyone or anything else
   同義詞：alone

副詞 only:

1. and nothing more
   同義詞：merely, simply, just, but
2. without any others being included or involved
   同義詞：entirely, exclusively, solely, alone
3. with nevertheless the final result
4. in the final outcome
5. except that
6. never except when
   同義詞：only if, only when
7. as recently as

1. Enjoy the disco you're only young once.
   盡情跳起迪斯科－－須知青春只一度。
2. I shall be only too pleased to get home.
   我要回到家里就非常高興。
3. The book is likely to be useful, only it's rather expensive.
   這本書(shū)可能有用，只是相當(dāng)貴。
4. He is the only person for the position.
   他是擔(dān)任此職位的最佳人選。
5. He speaks not only English but also French.
   他不但會(huì)說(shuō)英語(yǔ)，而且還會(huì)說(shuō)法語(yǔ)。
6. I saw him only yesterday.
   我昨天才見(jiàn)到他。

on.ly

adj.（形容詞）
Alone in kind or class; sole.
唯一的：在種類(lèi)或級(jí)別中與眾不同的；獨(dú)特的
Standing alone by reason of superiority or excellence.
出眾的：因杰出和優(yōu)秀而突出的
adv.（副詞）
Without anyone or anything else; alone:
單獨(dú)地：沒(méi)有其它別的事物；獨(dú)自地：
例句：
room for only one passenger.
單人客房

At the very least:
僅僅：
例句：
If you would only come home. The story was only too true.
只要你肯回家來(lái)。這故事是千真萬(wàn)確的

And nothing else or more:
只有，僅僅：
例句：
I only work here.
我只在這里工作

Exclusively; solely:
專(zhuān)門(mén)地，唯一地：
例句：
facts known only to us.
這些事只有我們才知道

In the last analysis or final outcome:
最后的分析，最終結(jié)果：
例句：
actions that will only make things worse.
最后使事情更糟糕的行為

With the final result; nevertheless:
最終結(jié)局，仍然：
例句：
received a raise only to be laid off.
加薪的結(jié)果只是被派遣而已

As recently as:
最近地：
例句：
called me only last month.
上個(gè)月剛通知我

In the immediate past:
剛才：
例句：
only just saw her.
剛才還看見(jiàn)她了

conj.（連接詞）
Were it not that; except.
假如；除非

With the restriction that; but:
條件是，但是：
例句：
You may go, only be careful.
你可以去，但要小心

However; and yet:
然而，畢竟：
例句：
The merchandise is well made, only we can`t use it.
這種商品做工精致，然而我們不能用

來(lái)源：
Middle English
中古英語(yǔ)
from Old English 3nloc
源自 古英語(yǔ) 3nloc
3n [one] * see one
3n [一個(gè)] *參見(jiàn) one
-loc [having the form of] * see -ly
-loc [具有這種形式的] *參見(jiàn) -ly

When used as an adverb,only should be placed with care to avoid ambiguity. Generally this means havingonly adjoin the word or words that it limits. Variation in the placement ofonly can change the meaning of the sentence, as the following examples show:
當(dāng)only 用作副詞時(shí)應(yīng)注意避免意義模糊。 一般來(lái)說(shuō)，這意味著把only 放在被限定詞的旁邊。 Only 的位置的改變， 會(huì)改變整個(gè)句子的內(nèi)容，例如：
例句：
Dictators respect only force;
獨(dú)裁者只認(rèn)同暴力；

例句：
they are not moved by words.
他們不會(huì)被言辭所打動(dòng)。

例句：
Dictators only respect force;
獨(dú)裁者只重視權(quán)力；

例句：
they do not worship it.
他們不崇拜它。

例句：
She picked up the receiver only when he entered, not before.
他剛一進(jìn)來(lái)她就接到了電話。

例句：
She only picked up the receiver when he entered;
她只在他進(jìn)來(lái)的時(shí)候接電話；

例句：
she didn`t dial the number.
她沒(méi)有撥電話。

Though strict grammarians insist that the rule for placement ofonly should always be followed, there are occasions when placement ofonly earlier in the sentence seems much more natural. In the following exampleonly is placed according to the rule:
雖然嚴(yán)格的語(yǔ)法學(xué)家主張應(yīng)該遵循only 位置的用法規(guī)則， 但有時(shí)only 放在的句子開(kāi)頭，看起來(lái)十分自然。 下面例子中only 的位置是按規(guī)則安排的：
例句：
The committee can make its decision by Friday of next week only if it receives a copy of the latest report.
委員會(huì)只有在收到最后的報(bào)告后，才可以在下周五作出決定。

Placement ofonly earlier in the sentence, immediately after can, would serve the rhetorical function of warning the reader that a condition on the statement follows.See Usage Note at not
Only 的位置緊跟在 can 的后邊且在句子開(kāi)頭， 可以利用倒裝句型提醒讀者后邊是一個(gè)條件參見(jiàn) not