Major form class and Word class

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

Word class and major form class are semantically related. In some cases you can use "Word class" instead a noun phrase "Major form class".

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

Major form class and word class are semantically related. Sometimes you can replace phrase "Major form class" with "Word class", this phrases are similar.