Many a/an + <singular noun>
is used to refer to a large number of things or people and usually stresses that number. It's rather formal and literary.
Note that it assumes the singular form and slightly differs from a more common variant "many + <plural noun>"
Many a tale was told.
Many a man has tried but few men have succeeded.
Any dictionary can be used for this.
For example, here's the entry for gravy on dictionary.com:
If you look up gravy it will lead you to this entry, telling you that gravy is a singular (or mass) noun.
If you look up gravies it will also lead you to this entry, telling you that gravies is the plural of gravy.
Essentially any dictionary or dictionary website ...
The sentence is awkward.
Drop “even the doctors,” and you get
No one thinks
which is obviously correct and idiomatic. “No one” is the subject and is singular.
When we add in “even the doctors,” we introduce a plural aspect that may suggest a plural verb. This is a grammatical mistake even though such mixtures of singular and plural fool even native ...
It should be populations in this instance because multiple officials are seeking multiple ways in multiple towns.
You can group multiple populations together and talk about them as one population for a particular purpose - for example, if there were a single project to increase the population over several towns and the results were to be measured for the ...
You could grammatically say any of
Profiles are functions of intensity with respect to wavelength.
Profiles are functions of the intensity with respect to the wavelength.
Profiles are functions of intensities with respect to wavelengths.
The first would be closest to defining what profiles are. The second would be about multiple profiles that depend on the ...
If you are asking whether to use an article "the", no article, or a plural, the best choice is the singular with no article. Since you've given a sentence fragment, it's hard to understand what is meant, but these would be possible expressions:
This is a plot of intensity as a function of wavelength.
This is a plot of intensity with respect to ...
You're one of the ones that understand(s) me
The native speaker was probably hypercorrecting. Note: I prefer "who".
A paraphrase should make it clear.
Of the ones who understand me, you're one.
We could expand it more
There are some 'ones' who understand me, and you are one of those ones.
The use of the singular implies that there is (or the author thinks there is) a single relationship between what might be called "emotional state" and disease, with "happiness" and "anxiety" being merely two possible values of a person's emotional state.