spacing
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?