What is the difference between "32 bar form", "song form", and "ternary" with a repeated first section?

Question

There are separate wikipedia articles for 32 bar form, but song form and ternary are in one article. From my understanding, repeats do not change the form in terms of classification, which is something emphasized by this article; yet the AP Barron's Music Theory Textbook says that "thirty-two bar song form" evolved from ternary with the first section repeated.

So what I'm confused about is: what makes song form, and "thirty-two bar song form" for that matter, different from ternary form? Is it the time period? Or are they equivalent or subsets of each other?

Answer 1

32-Bar form is a special case of ternary form that is so commonly used that it is deserving (at least in Wikipedia's estimation) of its own discussion

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Ternary form and song form are essentially two terms for the same thing. This is reflected in the Wikipedia entry:

Ternary form, sometimes called song form ... [emphasis original]

32-bar form is also a ternary form, but it is so commonly used — and rather specific to American "Tin-Pan Alley" music of the early 20th century — that it gets its own term.

Though the 32-bar form resembles the ternary form of the operatic da capo aria, it did not become common until the late 1910s. It became "the principal form" of American popular song around 1925–1926. (SOURCE: Wikipedia)

32-Bar form is specifically AABA with each section being 8 measures long. In general, however, the A and B sections of ternary form can be of any length, and they may or may not be repeated.