what if the subject and verb don't agree in number

[tianxiadaluan]

I'd like to know if the following sentence is grammatically correct: Table manners refers to the etiquette used while eating, which may also include the appropriate use of utensils.

Thx.

[2006]

Welcome!
How is my favorite city today?

I'd like to know if the following sentence is grammatically correct:

Table manners refers to the etiquette used while eating, which may also include the appropriate use of utensils.
"Table manners" could be considered to be singular, like a subject in school. But it could be considered to be plural.

I would treat it as plural, but I can't say that the sentence's treating it as singular is definitely wrong.

Thx.

2006

[Tdol]

Etiquette in the singular is the influence on this sentence I think- grouping all the different rules into a collective. Like 2006, I would generally use the plural- his table manners are dreadful.