I know that the word 広し means 広い, but which rule or grammar is included?


The sentence is from my textbook みんなの日本語

> 世界広しといえども ...

that means

> 世界が広いと言っても ...

right?

But what function has it when you use 広し instead of 広い?

During some research I found this [Website/ online
辞書](http://www.weblio.jp/content/%E3%82%AF%E6%B4%BB%E7%94%A8) but my Japanese
is not good enough to understand it.




### The basic grammar

The し ending on adjectives is the Classical Japanese 終止形【しゅうしけい】 or "terminal
form", i.e. the conjugation to use when the word comes at the end of a
sentence. The Classical Japanese 連体形【れんたいけい】 or "attributive form" (the
conjugation to use when modifying a noun or other substantive) is き. For
modern adjective 広い, the 終止形 and 連体形 are the same thing -- both end in い. For
Classical Japanese, the 終止形 is 広し and the 連体形 is 広き.

Classical Japanese forms still show up, especially when a writer (or more
rarely, a speaker) is trying to impart an archaic or more-formal feel. This
might be vaguely analogous to an English writer or speaker avoiding
contractions and restructuring sentences to avoid prepositions on the end
(such as replacing _" **who'd** you give it **to**?"_ with _" **to whom did**
you give it?"_). The Classical Japanese forms are even more archaic and formal
than this English example, but still understandable by modern speakers and
readers.

### The grammatical construction in your textbook

Looking at your specific textbook example, it's worth noting that this
construction of `[ADJ ROOT]` + し + といえども is a kind of somewhat-formal set
construction pattern. いえども itself is Classical Japanese for いっても, as you
correctly guess, and this Classical set-construction usage then influences the
conjugation of the adjective to also use the Classical conjugation. This is
not uncommon in written Japanese, but you generally won't hear this in spoken
Japanese, outside of rare contexts like speeches. In spoken Japanese, the
`[ADJ ROOT]` + い + といっても construction is much more common.




### The basic grammar

The し ending on adjectives is the Classical Japanese 終止形【しゅうしけい】 or "terminal
form", i.e. the conjugation to use when the word comes at the end of a
sentence. The Classical Japanese 連体形【れんたいけい】 or "attributive form" (the
conjugation to use when modifying a noun or other substantive) is き. For
modern adjective 広い, the 終止形 and 連体形 are the same thing -- both end in い. For
Classical Japanese, the 終止形 is 広し and the 連体形 is 広き.

Classical Japanese forms still show up, especially when a writer (or more
rarely, a speaker) is trying to impart an archaic or more-formal feel. This
might be vaguely analogous to an English writer or speaker avoiding
contractions and restructuring sentences to avoid prepositions on the end
(such as replacing _" **who'd** you give it **to**?"_ with _" **to whom did**
you give it?"_). The Classical Japanese forms are even more archaic and formal
than this English example, but still understandable by modern speakers and
readers.

### The grammatical construction in your textbook

Looking at your specific textbook example, it's worth noting that this
construction of `[ADJ ROOT]` + し + といえども is a kind of somewhat-formal set
construction pattern. いえども itself is Classical Japanese for いっても, as you
correctly guess, and this Classical set-construction usage then influences the
conjugation of the adjective to also use the Classical conjugation. This is
not uncommon in written Japanese, but you generally won't hear this in spoken
Japanese, outside of rare contexts like speeches. In spoken Japanese, the
`[ADJ ROOT]` + い + といっても construction is much more common.

