Is this headline a phrase or a sentence?

Question

This is a news report whose title is " 'Havana syndrome' not caused by foreign adversary, US intelligence says".

In my opinion, the title should be categorized as a noun phrase as in a "noun" + an "adjective clause" + a comma + somebody says. However, one of my friends said that it was a sentence in which an auxiliary verb could be absent because "you know, you can be creative in making a title". Perhaps I am wrong or I should enlighten him.

By the way, shouldn't the "adversary" be a plural noun like "adversaries"?

Answer 1

Headlinese has its own conventions that differ from those of "normal" English. The auxiliary verb "to be" and articles are often eliminated. Thus, the "original" sentence might be:

"Havana syndrome" [[is]] not caused by [[a]] foreign adversary, US intelligence says.

You can also analyze the first part of the headline (before the comma) as a noun phrase headed by "Havana syndrome"; the various constituents maintain fairly standard syntactic relationships. (I'd probably say "participial phrase" instead of "adjective clause", though.) Note that this is nevertheless still headlinese, since "normal" English requires a determiner for "foreign adversary" even if it is part of a larger noun phrase.

You could certainly say "foreign adversaries" instead of "[[a]] foreign adversary"; both are correct, and they have similar meanings in this context.

Answer 2

Newspaper headlines have many atypical, telegraphic conventions in English. This particular construction is basically just a way for the journalist to highlight the most important information by putting it first in the title.

The regular straight formulation would always be "US intelligence says [that] 'Havana syndrome' [was] not caused by [a] foreign adversary".

(In the old days, journalists were taught to write their story as an "upside down pyramid". The editor was expected to cut off a suitable amount from the end of the article to make it fit, and so the meat was supposed to go first, with less and less important and relevant information trickling down to the end, where it could be mercilessly removed without seriously hampering the general narrative.)

The unabbreviated version also explains, in a way, why "adversary" is singular. The conclusion is not that some foreign adversaries were not behind it (which would be rather vague), but rather the stronger statement that they rule out that any foreign adversary was involved.