动名词作定语和现在分词作定语的区别

动名词和现在分词，都可以作前置修饰语（premodifier）修饰名词。同样是“动词-ing形式”作定语，被修饰语和修饰语之间的关系是否一样？ “动词-ing形式”作定语时，被修饰语和它的关系可能是“目的或用途关系”，也可能是“主谓关系”， 这两种不同的修饰关系，是区分动名词还是现在分词的试金石。如果是前者，那么就是动名词作定语；如果是后者，那么就是现在分词作定语。

【动名词作定语】

动名词作定语，说明动名词和被修饰语是“目的或用途的关系”。所以，我们可以用for doing，used for doing，或者which is used for doing来置换这个动名词，放在被修饰语之后作定语。例如：

a swimming pool

①→ a pool for swimming

②→ a pool used for swimming

③→ a pool with the purpose of swimming

限于篇幅，以下词组仅用第①种情况转换：

a walking stick → a stick for walking

a sleeping car → a car for sleeping

a waiting room → a room for waiting

a swimming pool → a pool for swimming

a washing machine → a machine for washing clothes

a writing desk → a desk for writing

a reading room→ a room for reading

a bathing cap→ a cap for bathing

a changing room→ a room for changing clothes

a sitting room→ a room for sitting

a watering can→ a can for watering flowers

a guessing game→ a game for guessing words

an ironing board→ a board for ironing clothes

a collecting tin→ a tin for collecting money

a hiding place→ a place for hiding

a racing bicycle→ a bicucle for racing

an operating table→ a table for operating

building materials → materials for building

a diving board→ a board for diving

reading materials → materials for reading

a closing speech→ a speech for closing a meeting

working hours→ hours (time) for working

a smoking room→ a room for smoking

a dancing hall → a hall for dancing

a washing machine → a machine for washing clothes

【现在分词作定语】

现在分词作定语，说明被修饰语和现在分词是“主谓关系”。既如此，就可以扩展为一个定语从句，该定语从句多为进行时态。例如：

a sleeping baby → a baby who is sleeping.

a barking dog→ a dog that is barking

flying birds → birds that are flying

smiling faces →faces that are smiling

a floating boat → a boat that is floating

falling leaves → leaves that are falling

boiling water → water that is boiling

the setting sun → the sun that is setting

the rising sun → the sun that is rising

the coming week → the week that will come

the following questions→ the questions that follow

running water → water that is running

a developing country→ a country that is developing

the suffering people → people who are suffering

a missing child→ a child who is missing

现在分词短语作定语，都是置于被修饰语之后。单个的现在分词作定语跟动名词作定语，一般都置于被修饰词之前。正确判断是哪种形式作定语，有利于我们理解词组甚至整个句子的准确含义。

但有时这种区别并不明显，比如a sewing machine（缝纫机）可以理解为a machine for sewing，或者a machine which can sew; a hunting dog（猎狗）可以理解为a dog for hunting，或者a dog that hunts。前一种解释是看作动名词，后一种解释是看作现在分词。