How to determine whether the grammar is regular or not?

Question

If any grammer is given, how can we tell that the grammar is regular or not? Is that any perticular method?

Comments

If given grammer contain two or more than two variable in the production than yhe gramere will not br regular grammer

If grammer has production which  is either left linear or right linear both not both is always a regular grammer

Answer 1

Regular Grammar -:Type 3 Grammar and is of the form 

             $1.S\rightarrow aA\,$

            $1.S\rightarrow Aa\,$

Where $A,S \, \epsilon $ $Non\:Terminal$,

$a\epsilon\: Terminal$, But  NOT the combination of both.

eg-:

consider Production

$S\rightarrow aA$(right Linear/Regular Grammar)

$A\rightarrow Ab$(left Linear/Regular Grammar)

$A\rightarrow\varepsilon$

is not a regular grammar as it contains both Left and Right linear Grammar.

Comments

No it is linear grammar.

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So linear grammar cant be regular?

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when grammar is right linear as well left linear then grammar is not regular either it should be left linear or it should be right linear am i correct

Answer 2

there simple point to check wether the grammar is regular or not 

first point . If given grammar contain two or more than two non terminal  in the right hand side of production than the grammar will not  regular grammar 

second point. a regular language can have more than one grammar which can be regular or not regular 

take an example of regular language (a+b)(a+b)+

and grammar

S->AA

A->aA | bA | a | b 

here the language is regular but the grammar is not regular 

but you can generate at least one regular grammar for this language 

conclusion we can generate at least one regular grammar for every regular language 

third point . If grammar has production which  is either left linear or right linear but not both the the grammar is a regular grammar