consequent flexibility of English speech, words which are usually
other parts of speech are often used as nouns; and various word groups
may take the place of nouns by being used as nouns.

[Sidenote: _Adjectives, Conjunctions, Adverbs._]

(1) _Other parts of speech_ used as nouns:--

_The great_, _the wealthy_, fear thy blow.--BURNS.

Every _why_ hath a _wherefore_.--SHAKESPEARE.

When I was young? Ah, woeful _When_!
Ah! for the change 'twixt _Now_ and _Then_!
--COLERIDGE.

(2) _Certain word groups_ used like single nouns:--

_Too swift_ arrives as tardy as _too slow_.--SHAKESPEARE.

Then comes the "_Why, sir_!" and the "_What then, sir_?" and the
"_No, sir_!" and the "_You don't see your way through the
question, sir_!"--MACAULAY

(3) Any part of speech may be considered merely as a word, without
reference to its function in the sentence; also titles of books are
treated as simple nouns.

The _it_, at the beginning, is ambiguous, whether it mean the sun
or the cold.--Dr BLAIR