Form class and Major form class

Form class noun - One of the traditional categories of words intended to reflect their functions in a grammatical context.

Major form class and form class are semantically related. In some cases you can replace phrase "Major form class" with "Form class", this phrases are similar.

Major form class noun - Any of the major parts of speech of traditional grammar.

Form class and major form class are semantically related. You can use "Form class" instead a noun phrase "Major form class".