The noun is the only part of speech which has things belonging to it, that is, is given forms “fundamentally.” Where other parts of speech are given forms, these can be considered as forms of the noun.

For example, in the sentence: “The energetic man walked soberly towards the bright and crowded city with surprisingly undiverted purpose”—every word can be considered as a form of the noun man: the thing about which everything is said. The idea of subject in grammar has in it the idea of a thing to which all the forms in the sentence belong.

“The man walked.” The walked in the sentence implies an activity of the man, and can be seen as belonging to the man, that is, is a form of the man: for what we do belongs to us, is a form of us. The sentence would be complete as, “Man walked,” with walked as an active form of man. All the other words, singly or in phrases, modify the noun directly or the verb. In a sentence, there is an aggregate of forms and forms of forms. For example, in the phrase “with surprisingly undiverted purpose,” undiverted as participial adjective modifies purpose, and surprisingly modifies the modifier, or form, undiverted; while the whole phrase, noun and modifier and modifier of modifier, modifies the verb walked—which in turn, as I have said, is a form of the noun man. All the words after soberly are an adverbial phrase—that is, a “compound” adverb, which modifies, or is a form of walked. Soberly also, like the adverbial phrase or compound adverb, modifies walked.

Grammar should be seen as an interplay of forms. The human mind in grammar has flexibly caught up with the weavings of existence.