Warship types work better as spectra than boxes

What kinds of warship should be understood on a spectrum rather than in rigid categories?

Capital ships fall on a battleship-to-battlecruiser spectrum in this interpretation, tentatively extended to modern escorts.

A capital-ship spectrum places designs according to the balance they strike between battleship and battlecruiser characteristics. Designers seeking more protection for a battlecruiser can move it toward a fast battleship while still trying to preserve its speed. A ship can therefore sit nearer one category without losing every feature associated with another. The same approach is tentatively proposed for modern escorts, where rigid labels can obscure the mixture of characteristics in an actual design.