should/would/could've +pp（仮定法過去完了）

If you had trained more thoroughly, you could've completed the marathon.

thoroughly ソﾛｧ-ﾘ- adv)徹底的に

complete ｺﾝﾌﾟリ-ﾄ v)完全･完了する、仕上げる、申し分ないものにする

Had I known/I wish I had known/If I had known it would/was going to rain today, I would've brought my umbrella with me.

Had I known ( If の省略形）

I wish I had known 知っていればよかったのにな 

I wish I had known you were a good teacher, I could've taken your lesson more. 

文末にくる though

文末にくる though はカジュアルな副詞　butに言い換えられる
「～だけどね」「でも」「しかし」の意味

I think he is creepy. Only a bit, though.

（彼はキモいと思う。少しだけ。でも。）

Today was a fine day for football. It was chilly, though.
（今日は良い天気、フットボールに。少し寒かった、しかし。）
Today was a fine day for football. But it was chilly.

質問の回答としてよく使われる
Do you play the piano? - Oh yeah. I'm not so good, though.
（ピアノ弾く？　ええ。上手じゃない、けどね。）

creepy adj)気持ちの悪い
chilly　adj)（天候が）冷え冷えする

as long as / as far as

【接続詞】as long as ... 　...する間は《時間》=while
You can stay here as long as you want.
As long as he is here, I'm too nervous to eat anything.
(While he is here, I'm too nervous to eat anything.)

【接続詞】as long as ... 　...さえすれば《条件》=only if, provided
You can have a dog as long as you promise to take care of it.
I am happy as long as my family is happy.
(I am happy only if my family is happy.)

【接続詞】as far as... 　...する限り《程度･範囲》
As far as I'm concerned, you should not keep in touch with her anymore.
 concern v)...に関する、心配させる、不安にさせる

 As far as I'm concerned, 〔慣用句〕私としては、、（私に関する限りでは）
 As far as I know,　私の知っている限りでは
 As far as I (can) see,　私の見る限りでは
 As far as I (can) tell,  私の言える限りでは
 As fat as I (can) remember,  私の覚えている限りでは
 As far as the eye can see,　見渡せる限りでは
 As far as the eye can reach,　目が行き届く限りでは

As far as I remember, his name is Steven.
As far as I know, the marathon course is blocked with(by) fallen trees.
Well, as far as I remember, your name is...

theが付く最上級とtheが付かない最上級とは。。

theが付く最上級とtheが付かない最上級とは。。

A:Tom can swim fastest of the three.
B:Tom can swim (the) fastest of the tree.

両方正解だが文法セオリーとしては正解はA

【theは最上級に付くのではなく、最上級に修飾された名詞にtheが付く】 

（普通文で the が名詞の前に付くのと同じ発想 　ex. the bridge）

C:This is the tallest building in Osaka.　形容詞の最上級が名詞を修飾        

D:He is (the) brightest in his class.　形容詞の最上級が補語C

E:Tom can swim (the) fastest of the three.　副詞の最上級（副詞は動詞を修飾する）

文法的にはD、Eには the は付かないが言語は文法では説明できない習慣的な要素もあり the が付くことが実際に多い。またDでは brightest の後に student が隠れている（省略した）と考えれば the が必要になるので the を付けても間違いとは言えないことが理解できる。同様にEでは fastest の後に man が省略されていると考えることができる。

補足）下記2文の the は、いずれも名詞を修飾している

This is the tallest building in Osaka.

This is the surprising secret to a happy marriage.

（これはハッピーな結婚生活の驚くべき秘訣(secret)です）