n [U] amount of space left between objects, words, etc in laying or setting sth out （物体、字词等之间的）间隔, 间距
*Be careful with your spacing or you won't get the heading on one line. 注意间隔, 否则这个标题一行排不下.
* Shall I use single or double spacing (ie single or double spaces between the lines) when I type this letter? 我打这封信是用单行行距还是用双行行距?

n[U]
the amount of space between the printed letters, words, or lines on a page
single spacing
(=lines with no empty lines between them)
double spacing
(=lines with one empty line after each one)