bug#68375: 29.1; lispref documentation fixes

[Stephen Berman via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

On Fri, 12 Jan 2024 22:54:48 -0500 Richard Stallman <rms@gnu.org> wrote:

> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
>
>   > In this sentence "need" is not in the subjunctive mood but is being used
>   > as a modal verb, like "can", "must", etc.  What's special about "need"
>   > in this usage is that it only occurs in so-called polarity contexts
>   > (e.g. negative, interrogative), unlike the ordinary modal verbs (so
>   > e.g. "A buffer need be displayed" is ungrammatical but "A buffer
>   > can/must/may be displayed" is fine).
>
> Is there a grammatical name for this sort of verb usage practice?

If you mean the possibility of using an "ordinary" verb as a modal verb,
then I'm not aware of any term.  Maybe this is because this possibility
is so rare (at least in English; AFAIK the only other verb like "need"
is "dare").

If you mean the semantic restrictions on the use of "need" as a modal
verb, then AFAIK "polarity" is the most-widely used term (also in
compounds like "polarity-sensitive"), particularly within theoretical
linguistics but also in descriptive grammars like "The Cambridge Grammar
of the English Language".  (The phenomenon is much broader than the use
of "need", applying to the distributions of words like "any" and
"no(ne)", "ever" and "never" and so on.)

Steve Berman