Text Formatting ⇒ confused about \linewidth

[ghostanime2001]

I am confused about \linewidth. Some documents say it is the width of the current line in the current font. Do they mean the width of a sentence using the current text ? The definition seems too vague

[Stefan Kottwitz]

It's the width of the current line, that's correct. I would not speak about the font or a sentence. Changing the font or writing a longer sentence doesn't change the line width.

In a basic case, \linewidth means the width between the left margin and the right margin, so can be equal to \textwidth in a simple situation. However, in some situations the line is shorter, so \linewidth would have a smaller value, for example in lists such as itemize, enumerate and description, as you can imagine it would get even smaller within nested lists. It's the space which you can use on that line.

Stefan