When to use 是 and when not to use 是?

April 07, 2012, 02:54 PM posted in Grammar Questions

I get very confused on when to use 是 and when not to use it.  For example:

今天是我的妈妈的生日. You use the verb  是 in this phrase but then in a phrase like: 

我很好。The place where 是 should be is not there.

So, the question is: When do you use the verb 是and when don't you use the verb 是?

Profile picture
April 08, 2012, 02:24 AM

Usually when you have a pronoun (I, you, it etc) or noun (dog, book, table etc) and after is an adjective (good, fast, happy, smelly etc) then you do not use 是, but rather you use 很 or another adverb (非常,特别,太。。。了 etc) so for example:


wǒ hěn kāixīn


wǒ fēicháng kāixīn


wǒ tèbié kāixīn


wǒ tài kāixīn le


nà tiáo gǒu hěn chòu


Where as, when you say 今天是我妈妈的生日, you are saying what something IS, you are not describing it.  So for example:


nà běn shū shì wǒ de

他是一个很好的人 (contrast with 他很好)

tā shì yì ge hěn hǎo de rén


nǐ shì wǒ de lǎoshī ma


他是一个很好的人 he is a good person where as 他很好 just means he is good.

Hope that helps, if not just ask questions concerning my explanation!


Profile picture

多谢。 您的解释很好。我现在懂他。

Profile picture
April 08, 2012, 02:29 AM

是 is nessecary when you have a sentence that is logically A=B, and A and B are both nouns. Your example is 'Today=my mom's birthday' is this, nouns on both side of the equation. Chinese and english are the same in this respect, chinese would use 是 and english would use 'is' for the equal sign.

it is not nessecary when you have a noun followed by an adjetive. Ie, in your example 'I very good'. Now, in english we would put an 'am' between the two, but logically it is a different situation, and chinese does not see a need for this.

Chinese and english are mostly the same in not requiring a 'to be' expression when you have a noun followed by a verb, ie I run, he reads, they jump (there is of course the tense use of 'I am running' in english, but at least usually english is the same as chinese)

I've seen this difference explained as 'chinese adjetives also act as verbs' or some such, but this appears odd in treating the english case as some sort of standard that requires explanation for any deviation from - one could just as easily ask why english doesn't allow one to say 'I very good' and instead insists on throwing an 'am' inbetween the noun and adjetivie.

That's the basic explanation, below are a few side notes....

More detailed note 1: as you get more advanced you'll come across a complication, in that you sentence 我很好 will much less often appear as something like 我是很好的, ie a 是...的 expression will appear surrounding the adjetitive. This is not really an exception to the rule, but rather a special way of really emphasizing the condition, ie perhaps someone raised doubts as to whether you had a problem so you are saying 'but I really am fine!'. Another example might be someone might say something like 我现在是很好,但下个星期... because something bad might happen later, notice here we are just using 是 without a 的,and here the 是 is taking the role of drawing attention to the fact that you are about to sort of contradict the statement. There are alot of other conditions where you will find 是 used when there is no apparent need for it based on the basic rules, and in these cases it is doing something to the tone, over time it will feel natural. :)

Side note 2 - if you really want to understand why 是 developed in this way, ie only used for nounA=nounB sentences (apart from its later colloquial tone uses noted above), you just need to look at its development in the language. 是's original meaning was basically the same as the modern 这, it meant 'that,this' (it still means that in a few very formal modern uses, or in say the expression 是可忍,孰不可忍, which one will hear very occasionally).

At that early time in the language development, if you wanted to write A=B you would simply write AB也, ie you would just write the first noun, then write the second noun, then throw a 也 at the end. So this worked, but people found it could get rather confusing if the first noun A was pretty long. So they decided it would be easier to understand if they wrote 'A that B 也'. It's easy to see why this worked from an english example, take the sentence 'those guys who came over the other day and were really rude to all of us and then said we owed them money, they left town', now imagine you erased the word 'they', well it sounds less clear. So they started using the word 是, which meant 'they,it, this, etc' at the time for the same reason we do a similar thing in english.

Then overtime, people started looking at all these sentences that read A是B也, got tired of writing the 也, and then started thinking that the 是 sort of is something that means 'to be' rather than meaning 'this, that'. This change first demonstrated in rather colloqual writings, folk tales and ballads and the like, while the more formal writings and elites resisted for a time, but eventually it just seemed natural. And here we are today, where 是's original meaning is all but forgoten and the new use has taken center stage.

Thus, it is entirely natural that it is required between nouns, and not before verbs or adjetivies. ;)

Edit - haha, simultanous posts...well this way you'll have two different approaches to consult.

Profile picture