The w3schools like with many of its markup examples/explanations or definitions are usually inaccurate or poorly defined. Using some of those form examples would also lead to invalid markup. And there is a difference between XHTML and HTML forms unlike what they say. :nono:
Form "controls", is the correct generic term used for; buttons, checkboxes, radio buttons, menus, text input, file select, hidden controls and object controls and so forth.
Though typically if you use them in a sentence you would say which particular one you were talking about, e.g. checkboxes. If you were talking about a line of code you may then also refer to whether it was associated with INPUT, TEXTAREA or SELECT element, etc.