According to Aristotle, the concept of "causation" has to be understood in four different senses.
They continue with my emphasis in bold below:
The material cause is that out of which something is made or constructed; the formal cause refers to its internal structure; the efficient cause is that external agency from which the thing comes or originates; the final cause is the goal, function. or pur- pose of a thing.
When Aristotle applied this understanding of the four causes to man-made objects his analysis went as follows. A table, for example, is made of wood (material cause); it has the shape or form of a series of rectangles (formal cause); it was produced by a carpenter (efficient cause); and its purpose is to serve as a surface for such activities as eating and writing (final cause). The same analysis can be applied to natural objects. For example, in the case of an acorn, its material cause is the organic substances that compose it; its efficient cause is an oak tree, namely, the parent oak tree; its formal cause is its structural potential to become an oak tree; and the final cause is to become another oak tree.
Please see the titled question.
Why isn't an acorn's Formal Cause rather its physical shape, as photographed beneath?