1. An Introduction to Word Classes

2. Words are fundamental units in every sentence
my brother drives a big car
instinctively - brother and car are the same type of word
and also that brother and drives are different types of words.

3. brother and car belong to the same word class
brother and drives are different types, they belong to different word classes
We recognise seven MAJOR word classes: 
Verb
be, drive, grow, sing, think
Noun
brother, car, David, house, London
Determiner
a, an, my, some, the
Adjective
big, foolish, happy, talented, tidy
Adverb
happily, recently, soon, then, there
Preposition
at, in, of, over, with
Conjunction
and, because, but, if, or

4. Additional categories
articles < determiners
numerals
Types of verbs? 
Types of conjunctions?
Moreover, you'll find other additional categories along the way
for example, articles are generally taken to be a subset of a larger category called determiners. 
Some grammarians add a special category for numerals.
Additionally, these larger classes have subclasses; verbs can be regular verbs or irregular verbs. 
The category conjunction includes coordinating conjunctions and subordinating conjunctions.

5. Words are analyzed on the basis of their formation
The term parts of speech refers to an approach to classification of words
Words are analyzed on the basis of their formation
and their use in sentences (ex. noun?) 
what are the forms like? 
how are they used in sentences?
For example, noun refers to words that (usually) have singular/plural forms
and are used in sentences as subject, object, complement, etc. 
Of course, the descriptions of the features are more complex than my example

6. We use a combination of three criteria for determining the word class of a word:  
The meaning of the word 
The form or ‘shape' of the word 
The position or ‘environment' of the word in a sentence

7. 1. Meaning people places things house car David brother London
Using this criterion, we generalize about the kind of meanings that words convey.
For example, we could group together the words brother and car, as well as David, house, and London, on the basis that they all refer to people, places, or things.

8. It can also be applied to verbs
action
cook, drive, eat, run, shout, walk
It has also been applied to verbs
they denote some kind of "action", like cook, drive, eat, run, shout, walk.
In fact, this has traditionally been a popular approach to determining members of the class of nouns.

9. This approach has certain merits
It allows us to determine word classes by replacing words in a sentence with words of "similar" meaning.
My son cooks dinner every Sunday 
My son prepares dinner every Sunday 
My son eats dinner every Sunday 
My son misses dinner every Sunday
For instance, in the sentence My son cooks dinner every Sunday, we can replace the verb with other "action" words:
On the basis of this replacement test, we can conclude that all of these words belong to the same class, that of "action" words, or verbs. 

10. However, this approach also has some serious limitations
The definition of a noun as a word denoting a person, place, or thing, excludes abstract nouns
Similarly, to say that verbs are "action" words excludes a verb like be, as in I want to be happy.
such as time, imagination, repetition, wisdom, and chance
Although this criterion has a certain validity when applied to some words, we need other, more stringent criteria as well.

11. 2. The form or ‘shape’ of a word
Some words can be assigned to a word class on the basis of their form or ‘shape’.
-tion ending (ex.)
-able or –ible (ex.)
Many words also take what are called INFLECTIONS = regular changes in their form under certain conditions.
action, condition, contemplation, demonstration, organization, repetition
acceptable, credible, miserable, responsible, suitable, terrible
car -- cars  dinner -- dinners  book – books
walk -- walks -- walked -- walking

12. 3. The position or ‘environment’ of a word in a sentence
This criterion refers to where words typically occur in a sentence, and the kinds of words which typically occur near to them.
[1] I cook dinner every Sunday  [2] The cook is on holiday

13. Cook can be a verb or a noun -- it all depends on how the word is used.
She looks very pale   She's very proud of her looks
He drives a fast car   He drives very fast on the motorway  
Turn on the light   I'm trying to light the fire   I usually have a light lunch
(verb) - (noun) 
(adjective) - (adverb)
(noun) - (verb) - (adjective)

14. Of the three criteria for word classes that we have discussed here, the Grammar will emphasize the second and third - the form of words, and how they are positioned or how they function in sentences. 

15. Open and Closed Word Classes
Words are divided into grammatical classes, which are discriminated on the basis of three criteria:
semantic,
formal and
functional.

16. The semantic criterion deals with the most generalized meaning characterizing all the words in a class.
The formal criterion shows the specific word-building patterns and the grammatical forms of the words in a given grammatical class.
The functional criterion relates to the syntactic positions of words belonging to a particular class.

17. On the basis of these criteria, words are divided into
lexical classes
functional series of words
To the lexical classes belong the noun, the verb, the adjective, the adverb and the numeral.
To the functional series of words belong the article, the preposition, the particle, the pronoun and the conjunction.

18. Lexical classes
words of full nominative value with self-dependent syntactic functions
they are morphologically changeable units of language
these classes are OPEN
in the sense that they have a large number of members and can freely add new members

19. The class of nouns It is potentially infinite.
Example: Internet, website, CD-ROM, , newsgroup, modem, multimedia
it is continually being expanded as new scientific discoveries are made, new products are developed, and new ideas are explored
In the late twentieth century, developments in computer technology have given rise to many new nouns:

20. New verbs have also been introduced:
download, upload, reboot, right-click, double-click
The adjective and adverb classes can also be expanded by the addition of new words, though less prolifically.

21. Functional words
They are of incomplete nominative value and non-self-dependent functions in the structure of the phrase or the sentence.
They constitute CLOSED systems.
They are made up of finite sets of words which are never expanded.
they have few members and resist new additions

22. Word Classes Based on Meaning
For example,
generic vs. specific
stative vs. dynamic
assertive vs. nonassertive
In addition to creating word groups based on grammatical features, grammarians also create word groups based on meaning and the interactions between grammatical forms and these meanings. 

23. Generic & Specific
Generic vs. Specific is a way of explaining the meanings of nouns. 
A noun has "generic" meaning when it refers to things, people, ideas, etc., generally as types rather than as specific individuals. 

24. Generic Examples A computer is a machine.
The computer has changed modern life.
Computers are found just about everywhere.
Computation of grades is a process that computers handle efficiently.
Music can be played on computers.
For example, the nouns in the following sentences have generic reference:
Generic Examples

25. Specific Examples I got a new computer for Christmas.
I installed the new computer early in the morning of December 24.
I now own 3 computers.
Without Microsoft Excel on my computer, I would find the process of doing my grades really frustrating.
I play the music of Beethoven on my computers.
Specific Examples

26. The distinction between generic and specific meaning is a terrifically important concept
selection of the articles a/an and the and the decision not to use an article at all
a/an, the, and 0 articles are used for both generic meanings and for specific meaning
It lies behind one of the most difficult parts of English

27. In the above examples
The generic set is about computers in general--not about any particular computer owned by any particular person.
The specific set is about me and my computers in my home. 

28. If we approach teaching articles based on how they are used with different types of nouns, we would say something like:
a/an with singular nouns the with singular or plural or noncount nouns zero-article with plural or noncount nouns

29. Stative vs. Dynamic
a way of classifying different types of verbs--or at least different meanings that verbs can have
Stative refers to "state of being" rather than "action." 
She is a teacher.  He is a sociologist. 
(states of being rather than of activities)

30. Dynamic refers to "actions" and "activity" in verb meanings:
He walks to class. 
They eat lunch in the cafeteria.
The contrast is often used in ESL/EFL to help students understand why they can or cannot use a progressive verb form. 
That is, progressive verbs refer to actions rather than states of being. 

31. That's why this sentence is wrong:
*They are knowing English very well. 
The verb know generally is used for a "state of being" rather than an action, and so it can't be used in the progressive form (most of the time).

32. In ESL/EFL materials we have lists of verbs divided into groups of Stative Verbs and Dynamic Verbs. 
Actually:
some verbs are just about always used for stative meanings;
other verbs are just about always used for dynamic meanings;
but...verbs can be switched from one class to the other for special purposes. 

33. For example, verbs like taste or smell can be either actions or states of being: 
He was tasting the soup for salt when he dropped the box of salt in the pan. 
The soup tastes pretty salty now.

34. Assertive vs. Nonassertive
a way of talking about the difference between positive sentences and related negative sentences and questions.
positive sentences "assert" something
negative sentences and questions do not

35. Assertive Examples They have been to France already.
They had some French bread for dinner.
They saw somebody running out of the restaurant.

36. Nonassertive Examples
They haven't been to Egypt yet.
They haven't had any Egyptian bread yet.
Did they have any French wine?
Did they see anybody they recognized?
They didn't see anyone that they knew.