1. of the day, of a day
of the day每一天的'，當時的，當代的;
of a day暫時的，不長久的 eg:a famous scientist of the day
2. three of us, the three of us
three of us我們(不止三個)中的三個;
the three of us我們三個(就三個人)eg:The three of us---Tom, Jack and I went to the cinema.
3. by bus, on the bus
by bus表手段，方式，不用冠詞;
on the bus表範圍 eg:They went there by bus.
4. for a moment, for the moment
for a moment 片刻，一會兒;
for the moment暫時，一時 eg:Thinking for a moment, he agreed.
