Different definition, or not include in the dictionary
Different generations in the same country speak different "languages"? Sounds impossible, but it is indeed the case. Consider situations in which your mother does not understand what you say to your classmates, situations in which you cannot figure out what your mother refers by a simple abbreviation and situations in which your father cannot reflect your undertone of some words. Different generations speak different "languages", causing conflicts and misunderstandings.
According to the passage "What can words do and cannot do", words have denotative meanings and connotation meanings. Denotative meanings are meanings defined by the dictionary, which cause little misunderstandings. On the other hand, connotative meanings are associated with personal experiences and are likely to cause conflicts. But in the context of communication between different generations, there are both likely to evoke misunderstandings.
Some connotative meanings of words are so widely recognized by a certain generation or group of people, that they consider these meanings as denotative meanings. But these meanings are unknown to other groups and are not included in the dictionary. The word, "net", for example, may mean "a trap made of netting to catch fish or birds or insects" in your grandfather's dictionary but means "a computer network consisting of a worldwide network of computer networks that use the TCP/IP network protocols to facilitate data transmission and exchange" when you talk to your friends meet on the "net". From this aspect, language of different generations do differ in the conception of words.
Different generations may be confused by denotative meanings, not to mention by connotative...