Ragas can be classified using different criteria. Here are a few classifications:
Number of Notes
Sampurna (Complete) Ragas : Ragas that contain all 7 notes of the octave are called Sampurna Ragas.
Shadav Ragas: Ragas that contain 6 notes of the octave in the scale are called Shadav Ragas.
Aurav Ragas: Ragas that contain 5 notes of the octave in the scale are called Audav Ragas.
The ragas are further named based on the number of notes in the Arohana (ascent) and the Avarohana (descent) of the scale.
Aurav - Aurav: The raga contains 5 notes in arohan and 5 notes in avarohan
Aurav - Shadav: The raga contains 5 notes in arohan and 6 notes in avarohan
Aurav - Sampurna: The raga contains 5 notes in arohan and all 7 notes on avarohan
Similarly we have ragas as Shadav-Aurav, Shadav-Shadav, Shadav-Sampurna, Sampurna-Aurav, Sampurna-Shadav, Sampurna-Sampurna
Based on Time
All ragas are divided into two groups as Poorva Ragas and Uttar Ragas.
Poorva Ragas: Poorva Ragas are sung between noon and midnight
Uttar Ragas: Uttar Ragas between midnight and noon.
Pricipal Raga Classification (6 Ragas, 36 Raginis)
Another division of ragas is the classification of ragas under the principal ragas:
The raga-ragini scheme is a classification scheme used from the 14th century to the19th century. It usually consists of 6 'male ragas each with 'wives' (raginis) and a number of sons (putras) and even daughters-in-law. As it did not agree with various other schemes, and the 'related' ragas had very little or no similarity, the raga-ragini scheme is no longer very popular. However, they define a very important fact of Indian Classical Music and the Raga system is that the ragas do have personality and can be imagined to have relationships with each other.
These are listed is as follows
(1) Bhairav raga
Wives: Bhairavi, Bilawali, Punyaki, Bangli, Aslekhi. Sons: Pancham, Harakh, Disakh, Bangal,Madhu, Madhava, Lalit, Bilaval.
(2) Malkaus raga
Wives: Gaundkari, Devagandhari, Gandhari, Seehute, Dhanasri. Sons: Maru, Mustang, Mewara, Parbal,Chand, Khokhat, Bhora, Nad.
(3) Hindol raga
Wives: Telangi, Devkari, Basanti, Sindhoori, Aheeri. Sons: Surmanand, Bhasker,Chandra-Bimb, Mangalan, Ban, Binoda, Basant, Kamoda.
(4) Deepak raga
Wives: Kachheli, Patmanjari, Todi, Kamodi, Gujri. Sons: Kaalanka, Kuntal, Rama, Kamal,Kusum, Champak, Gaura, Kanra .
(5) Shree raga
Wives: Bairavi, Karnati, Gauri, Asavari, Sindhavi. Sons: Salu, Sarag, Sagra, Gaund,Gambhir, Gund, Kumbh, Hamir.
(6) Megh raga
Wives: Sorath, Gaundi-Malari, Asa, Gunguni, Sooho. Sons: Biradhar, Gajdhar, Kedara,Jablidhar, Nat, Jaldhara, Sankar, Syama.
Thaat System of Classification
An important way of Raga classificationis the Thaat system. A certain arrangement of the seven notes with the change of shuddha, komal and teevra is called a Thaat. Every raga has a fixed number of komal or teevra notes, from which the thaat can be recognised. There are several opinions in this matter. According to Pandit V.N. Bhatkhande, the 10 thaat's used to classify ragas are
1 Bilaval : All shuddh or natural notes.
2 Khamaj : With ni note as komal.
3 Kafi : With ga, ni as komal.
4 Asavari : With ga, dha, ni askomal.
5 Bhairavi : With re, ga, dha, ni askomal.
6 Bhairav : With re, dha as komal.
7 Poorvi : With re, dha as komal andma as teevra.
8 Todi : With re, ga, dha as komaland ma as teevra.
9 Marwa : With re as komal and ma asteevra.
10 Kalyan : With ma as teevra only.
Based on Rasa (Emotion)
Bharata Muni enunciated the eight Rasas in the Natyasastra,an ancient work of dramatic theory. Each rasa, according to Natyasastra, has a presiding deity and a specific colour. The aura of a frightened person is black, and the aura of an angry person is red. Bharata Muni established the following.
Sringaram - Love, attractiveness. Presiding deity: Vishnu. Colour: light green
Hasyam - Laughter, mirth, comedy. Presiding deity: Pramata. Colour: white
Raudram - Fury. Presiding deity: Rudra. Colour: red
Karunyam - Compassion, mercy. Presiding deity: Yama. Colour: grey
Bibhatsam - Disgust, aversion. Presiding deity: Shiva. Colour: blue
Bhayanakam - Horror, terror. Presiding deity: Kala. Colour: black
Viram - Heroic mood. Presiding deity: Indra. Colour: yellowish
Adbhutam - Wonder, amazement. Presiding deity: Brahma. Colour: yellow
A ninth rasa was added by later authors. This addition had to undergo a good deal of struggle between the sixth and the tenth centuries, before it could be accepted by the majority of the Alankarikas, and the expression Navarasa (the nine rasas), could come into vogue.
9. Santam - Peace or tranquility. deity: Vishnu. Colour: blue
Classification of Ragas give out a number of important messages for all artists and students and listeners of the ragas:
a. Ragas have personality and emotion
b. They have relationships with each other
c. Ragas are closely related to nature and time of the day or season of the year
d. They canh be associated with colours and moods
e. It is highly related to spirituality
The artist of Indian Classical Music while performing tries to bring out all these aspects of the raga and this is what makes Indian Classical Music so intense and spiritual in nature.