Ghazal is a collection of Sher's which follow the rules of 'Matla', 'Maqta', 'Beher', 'Kaafiyaa' and 'Radif'.
For example:
1. koi ummid bar nahi aati koi surat nazar nahi aati.
2. aage aati thi haale dil par hasi ab kisi baat par nahi aati
3. hum waha hai jaha se hum ko bhi kuch hamari khabar nahi aati
4. kaaba kis mu se jaoge Ghalib sharm tumko magar nahi aati
'Sher'
A 'Sher' is a poem of two lines and every Sher in itself is a poem. So the four stanzas in the above example are independent poems or Sher. Ghazal is a collection of two line poems called Sher.
'Beher'
'Beher' is the 'meter' of the Sher's. It can be considered as the length of the Sher. Both the lines in the Sher *MUST* be of same 'Beher'. And all the Sher's in one Ghazal *MUST* be of the same 'Beher'. There are 19 (!!) kinds of 'Beher'. But in simple terms, 'Beher' is categorized in 3 classes. Short, medium, long.
For example:
Small : ahale dairo-haram reh gaye tere deewane kam reh gaye [ Also Talat song, "dil-e-nadan tuze hua kya hai" ] Medium : umr jalwo me basar ho, ye zaruri to nahin har shab-e-gam ki seher ho, ye zaruri to nahin [ And by Gulzar, "ruke ruke se kadam, ruk ke baar baar chale" ] Long : ai mere humnashin, chal kahin aur chal, is chaman me ab apanaa guzaaraa nahin baat hoti gulon ki, to seh lete hum, ab to kaaton pe bhi haq hamaaraa nahin [The filmfare winner, "Manzile apani jagah hai" !! Yes! It IS a Ghazal. And the Shayar is Prakash Mehra !! surprise, surprise !! ]
'Radif'
In a Ghazal, second line of all the Sher's *MUST* end with the *SAME* word/s. This repeating common word is the 'Radif' of the Ghazal. In our example, the 'Radif' is "nahin aati". [Sometimes, the Ghazal becomes known by its 'Radif'. eg. "jaraa aahista chal" sung by Pankaj Udhas. On RMIM we all know one Ghazal by the 'Radif' as "aahista aahista", don't we? Or is it 2 or 3?]
'Kaafiyaa'
'Kaafiyaa' is the rhyming pattern which all the words before 'Radif' *MUST* have. In our example the 'Kaafiyaa' is "bar", "nazar", "par", "magar" etc. This is a necessary requirement. Something which is followed even in the exceptions to all these rules.
'Matla'
The first Sher in the Ghazal *MUST* have 'Radif' in its both lines. This Sher is called 'Matla' of the Ghazal and the Ghazal is usually known after its 'Matla'. There can be more than one 'Matla' in a Ghazal. In such a case the second one is called 'Matla-e-saani' or 'Husn-e-matla'. In our example, the first Sher is the 'Matla'.
'Maqta'
A Shayar usually has an alias ie. 'takhallus' eg. Mirza Asadullakhan used 'Ghalib' as his 'takhallus' and is known by that. Other examples are 'Daag' Dehlvi, 'Mir' Taqi Mir, Said 'Rahi', Ahmed 'Faraz' etc. There is a Sher in a Ghazal, the last one, which has the Shayar's 'takhallus' in it. [ A Shayar, can use the 'Maqta' very intelligently. He can "talk to himself" like one in our example. I have lots of favourite Sher's which are 'Maqta' of some Ghazal. Some gems are koi nam-o-nishan puchhe to ai kaasid bataa denaa, takhallus 'Daag' hai, aur aahiqon ke dil me rehte hai and jab bhi milte hain, to kehte hain, "kaise ho 'Shakil'", iske aage to koi baat nahin hoti hai The first one uses the meaning of the 'takhallus' to create the magic, and the second one is just simple, simply beautiful. ] To summarize, Ghazal is a collection of Sher's (independent two-line poems), in which there is atleast one 'Matla', one 'Maqta' and all the Sher's are of same 'Beher' and have the same 'Kaafiyaa' and 'Radif'.
Exceptions and Important points:
1. Ghazal is just a form. It is independent of any language. eg. in Marathi also, there can be (and there are) good Ghazals.
2. Some Ghazal's do NOT have any 'Radif'. Rarely. Such Ghazal's are called "gair-muraddaf" Ghazal.
3. Although, every Sher, should be an independent poem in itself, it is possible, that all the Sher's are on the same theme. What famous example can be other than "chupke chupke raat din aasun bahaanaa yaad hai".
4. In modern Urdu poetry, there are lots of Ghazal's which do NOT follow the restriction of same 'Beher' on both the lines of Sher. [ My example in 'Maqta', the Sher by Shakil, is one. ] But even in these Ghazal's, 'Kaafiyaa' and 'Radif' are present.
5. The restriction of 'Maqta' is really very loose. Many many Ghazal's do NOT have any 'Maqta'. [I think 'Maqta' was used in the earlier times, as a way to keep the credit. But since this is traditional, many Ghazal's do have a 'Maqta' just for the sake of it. Sometimes the name of the Shayar comes unnaturally in the last Sher of the Ghazal. ]
Ghazal rudaad hai naakaamiyon ki, Ghazal mehrumiyon ki daastaan hai | Ghazal riste hue zakhmon ka marham, Ghazal ek chaaraa-e-dard-e-nihan hai | Ghazal ka husn hi hai, husn-e-aalam, Ghazal ka noor hi noor-e-jahan hai | - Jagdish Bhatnagar 'Hayaat'
