Hot answers tagged nouns
A slice is always a piece, but a piece is not always a slice. In general, a slice is a portion created with a single cut, and either it is wedge-shaped, or it is relatively thin in one of its dimensions because it is a cross-sectional cut of a much longer object; while a piece is a portion created by any means at all (cutting, tearing, shattering, biting, ...
In your phrase, hidden layer is an attributive noun: it's a noun which behaves as an adjective modifying sizes. In English, adjectives are not inflected for number; that is, the form of an adjective doesn't change depending on the number of what it's describing. [This differs from French, for example.] One red apple Two red apples Thus your ...
I would opt for hidden layer sizes. I'm guessing the label is for a table or graph and you're labeling a list of different sizes. Since you're showing multiple sizes, so you pluralise "size". "Hidden layer" is simply a specifier; it specifies the things that have the sizes that you are showing. @FumbleFingers makes a very good point in the comments: ...
The Oxford English Dictionary dates this usage to 1580 (another early citation is Shakespeare's Love's Labours Lost, act II, scene i). It describes it as "chiefly poetical".
Both versions are equally grammatical and mean the same thing. The version without is is a simple ellipsis of the version with it.
Only top voted, non community-wiki answers of a minimum length are eligible