Basically, it's usually a good idea to
- use clear and concise language that accurately describes the button's
action
- avoid generic labels like "Submit" or "Click here." Instead,
use more descriptive labels like "Sign Up" or "Download Report."
- make sure the button label is easily readable, both in terms of font size
and color contrast.
- provide additional context using ARIA labels or other
techniques.
For each purpose, do what is needed, it should not be about the count of words or the length of the label, it's all about your buttons being clear and understood as fast as possible.
Here's what different design systems say about button labels, hope it helps:
To use text, create a short label that succinctly describes what the
button does. Using title-style capitalization, consider starting the
label with a verb to help convey the button’s action — for example, a
button that lets people add items to their shopping cart might use the
label “Add to Cart.”
A button’s text label is the most important element on a button, as it
communicates the action that will be performed when the user interacts
with it. Buttons need to be clear and predictable.
Button labels should clearly indicate the action of the button. To
provide enough context, use the {verb} + {noun} content formula on
buttons except in the case of common actions like “Done”, “Close”,
“Cancel”, “Add”, or “Delete”.
There are exceptions to this rule for situations in which button
length could cause problems in compact UIs or negatively impact
translation, but the {verb} + {noun} formula is still best practice.
Here are some suggestions for action label texts
They don't talk too much about the length of the labels, but there's this "don't" part:
Avoid text labels that are too long. They should be concise.
Note that in Material Design version 3 aka Material 3 they don't recommend using all-caps labels anymore.