现在分词和过去分词的主要区别在于：现在分词表主动意义;过去分词表被动意义。
现在分词较过去分词形式灵活，除部分能接宾语之外，可有被动形式(being done)和完成式(having done， having been done)， 当然being done和having been done也可理解成过去分词变形为进行式
1. 现在分词作定语
现在分词常接在名词之后作定语，经常可与定语从句替换
如：the man sitting behind me， 相当于：the man who is sitting behind me
the kids running about in the garden， 相当于：
the kids who are running about in the garden
单个的分词作定语可放在被修饰词之前，如：the sleeping baby， a running nose
改错题中若出现名词之后直接接动词，且之间是主谓关系，但不是句子主谓语，此处必定有错，可改为现在分词作定语
例题：
(1)
The boiled point of any liquid is determined by the pressure of the surrounding gases.
应改为：boiling.
解释：沸点的英文表达应该是boiling point. 类似的表达如： boiling water(沸水); boiled表示已完成的状态， 如boiled water意为白开水， 即已沸腾过的水
(2)
The slide rule uses sliding scales with marks ---- numbers and their logarithms.
(A) representing
(B) represented
(C) are represented
(D) they are representing
答案：A
解释：空格前是句子的主谓成分，空格处需要marks的定语，C， D可先排除;B是被动式，无法接宾语numbers; 因此A正确，是现在分词作定语
2. 现在分词作状语
分词还可在句中作状语，可放在句首、句中或句尾。现在分词作状语时，通常都表示主语正在进行的动作/伴随动作或者表示原因。
1.现在分词短语可以作时间状语，相当于when， while， as soon as等所引导的从句
如：Hearing the news， he couldn’t help crying.
= When he heard the news， he couldn’t help crying.
2.现在分词短语也可以表示原因，代替由since， as等所引导的从句
如：Not knowing what to do about the situation， she turned to him for help.
=Since she didn’t know what to do about the situation， she turned to him for help.
Being so poor in those days， we couldn’t afford to go to school.
=As we were so poor in those days， we couldn’t afford to go to school.
3.如果分词表示的动作发生在主句动作之前，那么此时分词就需要用完成形式
如：Having finished the work， she went to the park.
=After she had finished the work， she went to the park.
特别注意：分词状语的逻辑主语和句子的主语要保持一致
如： Seeing from the moutain， the ocean is emrald green.
此句是一个错误的句子， 因为根据分词状语的逻辑主语和句子的主语要保持一致的原则， seeing的逻辑主语也应该是the ocean， 而the ocean是不能自己seeing的， 应改为Seen from the mountain.
例题：
(1)
Snow aids farmers by keeping heat in the lower ground levels， thereby ---- from freezing.
(A) to save the seeds
(B) saving the seeds
(C) which saves the seeds
(D) the seeds saved
答案：B
解释：thereby一词习惯上接现在分词作句子的结果状语，只有B符合要求