Perhaps the first words that we would want to learn in any language would be "yes" and "no". This is made fairly simple for people learning a Germanic or Romance language because not only are the words used almost identically as far as sentence structure goes, but also they have the same words, more or less.
So for people who want to learn Chinese, these might be the first two words we would want to learn. However, there are no words that mean "yes" or "no" in Chinese. The reason for this is clear:
The Chinese people live in a holistic reality that is beyond such Western dualisms as "yes" and "no", preferring to see the world as a gradiant of interlocking metaphorosis, rather then as a logical either/or dichotomy Even in English, "yes" or "no" are grammatically fairly hazy. "Yes" or "no" do not make a full sentence. They are only used as a type of particle to affirm or deny the previous statement made.
There are, however, words that roughly compare to English words for "yes" and "no". The closest word to "yes" in Chinese is shi the verb that means to be. Thus, if someone asks if such and such a condition is true, the answer could be, quite simply shi, "it is". Another word that fits for general purposes is dui "true", which can also be used to affirm any question posed. However, beyond this, the easiest way to say "yes" in Chinese is just by using the appropriate verb for the sentence. For example, if asked ni yao chi wufan ma "do you want to eat lunch", the best response may be yao "want"; or even by answering the entire question in the affirmative.
Words for "no" are a little more tricky. Their are several words for negation in Chinese, such as bu, mei, bie (不, 沒, 別) but all of them are adverbs, used only to modify verbs. "Bu", the most common negation in Chinese, has almost no meaning by itself, somewhat like English "not". You can say someone is bu pao "not running", but you can not say that they are bu "not". This being said, the easiest way to say "no" in Chinese is by taking the ways of saying "yes", and then negating them using "bu" or another negating adverb. So, bu shi "Not is", or bu dui "not true", or, again, bu followed by whatever verb is appropriate.
Thus, even though at first it might seem a language can not survive without such simple words as "yes" and "no", we see that Chinese manages to do well, and perhaps be a bit clearer, without them.