1 在某些名词词组前，可以省略。如(in) that day, (on) Mondays, (in) the year before last
2 在of + 形状、大小、年龄、面积、材料结构中，of常省略。
如When I was (of) your age, I knew much less than you.
The desks in our class are (of) the same color, material, shape, height and length.
如He has been waiting for you (for) a whole afternoon.
如You can wear that outfit in summer and (in) winter.
A The children were interested in and disgusted by the movie.
B It was clear that this player could both contribute to and learn from every game he played.
C He was fascinated by and enamored of this beguiling woman.
5 在某些习语中的省略。如be busy (in) doing sth, (in) … way …, next (to) , have difficult / trouble (in) doing sth, stop … (from) doing sth, spend … (in) doing sth opposite (to),
have a good time (in) doing sth, waste …(in) doing sth, pass time (in) doing sth
kill time (in) doing sth, (in) this / that way, (at) any time, near / nearer / nearest (to)
prevent / stop …(from) doing sth, It’s (of) no use (in) doing sth