下一节目五分钟後开始，现在先播放些音乐。 The next programme starts in five minutes: in the meantime, here's some music.
我因有约在先，所以未能参加这个会。 I was unable to attend the meeting because of a prior engagement.
有约在先，我恐怕不能与你共进晚餐。 I fear that a prior engagement will prohibit me from joining you in dinner.
在先，居前在时间上居前或来得早 A preceding or coming earlier in time.
回针缝在先前缝的一针中间加缝的一针，以便使针脚的交错重叠为原来长度的一半 A stitch made by inserting the needle at the midpoint of a preceding stitch so that the stitches overlap by half lengths.