
The Japanese, upon coming into contact with the art of Bonsai, "regulated" the forms in which they were created, in order to "simplify" their aesthetic evaluation.
These rules, commonly called "classic Japanese styles," also served to simplify and ensure the aesthetic maintenance of Bonsai across generations.
These styles are inspired by the shapes that trees create in nature, perfected in detail through the Bonsai technique.
Although there are many more, and various derivations of each, we will try to briefly describe some of the main "classic Japanese styles".
Hokidashi (Japanese name) - Tree with a rounded crown, usually with a straight trunk; we can see it in nature in various species and locations (e.g., orange tree).

Moyogi - Informal upright, a tree whose trunk presents several curves with branches on the outer side of each curve.
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Chokan - Formal upright, a tree with a straight trunk, with several branches distributed around it.

Fukinagashi - Wind-swept, we easily see trees in nature take this form near coastal areas with prevailing winds from the sea side.

Yose–eu - Forest, a group of several trees of the same species, with different heights and trunk thicknesses harmoniously combined.

Sekijojo - Clinging to the rock, a plant whose roots “embrace and engulf” a rock forming a deeply balanced ensemble; in this style, the plant feeds on the soil found in the pot beneath the rock.

Is-hitsuki - Planted on the rock, one or more plants planted on a rock that serves as their pot as it contains soil in cavities within the rock itself.

Kengai - Cascade, a plant whose apex grows downward; it is common to see trees in nature acquire this shape when growing on mountains where the weight of snow and wind cause them to grow downward, protecting themselves by the mountain slope.

Han-kengai - Semi-cascade, in this style it is the first branch that extends downward, having a dominant movement over the apex.

Sharimiki - Plant with several deadwood areas; in this style, more important than the shape of the Bonsai (which can even be included in another style) is the amount of dead areas on the trunk (shari), as well as dead branches (jin), normally representing a very old tree battered by climatic conditions.
Neagari - Exposed roots, in this style the base of the plant is composed of several exposed roots, as if due to soil erosion and constant flooding.

Bunjingi - Literati, owes its name to the “Scholars,” artists who isolated themselves in the mountains to find inspiration, and later painted in their books and paintings trees with these shapes acquired by growing in harsh conditions at mountain tops. It is a style of fluid lines where the green mass has only a small representation. These are Bonsai in which the strong line is the height and where emptiness predominates.

Often, more than one style can be found in a single tree, and not all Bonsai need to fit into one of these styles; even in nature there are trees with shapes that do not fit into any style.
In summary, if our Bonsai does not have the form of a classic "Bonsai" (classic style), it can always be a perfect miniature tree.