Most human languages are transmitted by sounds and one of the most obvious differences between languages is that they sound di

Word classes 
The basis of syntax is the fact that the words of a language come in different classes or 
parts-of-speech — nouns, verbs, adjectives, prepositions and so on. Not all languages 
have the same classes (English has articles like an and the showing that a noun phrase is 
indefinite or definite respectively, Japanese does not), and the same basic meaning can be 
expressed in different classes in different languages (thus the most basic words 
corresponding to most kinship terms in the Yuma language of California are verbs; to say 
‘I am his younger brother’, you say literally something like “he younger-brother-calls 
me”, where the equivalent of ‘younger-brother-call’ is a single verb morpheme). We 
establish the word classes and which words are in which class on the basis of the way 
words behave. For example, in English there is a class of words that take an inflection to 
show past tense (walked, strolled, ran) and another class which can follow the word the 
at the end of a sentence (I saw the book/table/boy). 

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Having established the word classes for a particular language, we can then label them.
There is always a class which contains most of the words referring to concrete objects, 
and we call that class ‘nouns’. Likewise, there is always a class which contains most of 
the words referring to actions, and we call that class ‘verbs’. It is important to note that 
the precise list of words which are in any class may differ from language to language; as 
we noted above, the word corresponding to ‘brother’ in Yuma is a verb, and while 
excitement is a noun in English, it does not refer to an object. So we cannot say that 
nouns are words referring to things; rather a noun is any word which is in that class, 
defined in terms of language-specific behaviour, which happens to include most words 
referring to things (and other words as well). 
Many languages also have subclasses within each class. For example, while all verbs in 
English show marking for tense, they can be distinguished by how many nouns (or