Reviewing superlatives -- 最上級を復習 (updated)

The key for superlatives is "most". "Most" by itself means the greatest number or measure:

最上級の秘訣は "most" です。単独にしては "most" は一番多い、最上の数及び量を示している。

• most people 人のもっとも多い（数）
• most money お金のもっとも多い（量）
• most ideas 発想のもっとも多い（量）

It can also be used with adjectives:
形容詞に合わせることも可能です。

• most tall もっとも（背の）高い
• most short もっとも（背の）短い
• most heavy もっとも重たい
• most light もっとも軽い
• most interesting もっとも興味を起こす（興味有る）
• most fun もっとも面白くて楽しい
• most funny もっとも可笑しい
• most disgusting もっとも嫌がらせる（嫌な）

And it can be used with adverbs:

また、副詞に合わせることもできます。

• most quickly もっとも素早く
• most slowly もっともゆっくりと
• most carefully もっとも注意深く

Many relatively short adjectives combine with most:

まあまあ短い形容詞の多くは "most" と組み合わせることができます。

• tallest
• shortest
• heaviest
• lightest
• interestingest (too long and clumsy)（長くて言いにくい）
• funnest (*Preferred form is "most fun".) （普段の形は "most fun" です。）
• funniest
• disgustingest (too long and clumsy)（長くて言いにくい）
• quickliest (adverbs don't) （副詞はできません。）
• quickest もっとも素早い
• slowliest (adverbs don't) （副詞はできません。）
• slowest もっともゆっくりした
• carefulliest (adverbs don't) （副詞はできません。）
• carefullest (too long and clumsy)（長くて言いにくい）
• most careful もっとも注意深い

The shorter form is usually preferred. In the case of "fun", there can be confusion with "funny", so "most fun" is usually preferred.

大抵は短い方が優先されるけど、"fun" の場合は "funny" との矛盾が生じるので "most fun" の方を普段に使っています。

To make the superlative truly unique, we indicate it with "the":

唯一の最上空であると指定したい時は "the" を使って指摘します。

• the tallest tower in the world
• the shortest river in Japan
• the heaviest airplane in the air
• the lightest car on the road
• the most interesting subject at school
• the most fun way to spend a Saturday
• the funniest comedienne in the school
• the most disgusting food that she had ever eaten
• run the most quickly (or, run the quickest)
• walk the most slowly (or, walk the slowest )
• set the table the most carefully

The superlative phrase is generally used as a unit:

最上級の文は一般的に一塊として使えます。

• Is Sky Tree the tallest tower in the world?
• What is the name of the shortest river in Japan?
• I read a magazine article about the heaviest airplane in the air today.
• Three automobile manufactures announced a competition to design the lightest car on the road.
• English is not the most interesting subject at school for me.
• But English class is the most fun way to spend a Saturday.
• Junko is the funniest comedienne in the school.
• She said that natto was the most disgusting food that she had ever eaten.
• Harumi ran the most quickly to the goal line.
• Joel walked the slowest of all.
• Chieko set her table the most carefully.

There is an inverse superlative, but the grammar for it is simpler. "Less" never combines:
最低級と言える形もあります。最上級よりも簡単です。組み合わせても別々の単語です。

• least tall
• least short
• least heavy
• least light
• least interesting
• least fun
• least funny
• least disgusting
• least quickly
• least slowly
• least carefully

And, finally, "good" and "well" are irregular in their combined form, the superlative of both is "best".

最後に、 "good" も "well" も組み合わせた形には不規則なのに、双方の最上級は "best" になります。

Mark is my most interesting friend. He is also my best friend.

I guess I should also mention "bad" which is also irregular in the superlative form -- "worst".
ところで、 "bad" も最上級が不規則にして "worst" となります。

 I had the worst nightmare last night. （"nightmare" == 「悪夢」）

I think these are the basics of superlatives.
これが最上級の基本とボクは思っています。