Because the Tipitaka is a large collection of scriptures. Traditionally, it is said that there are 84,000 chapters within the Tipitaka, but no one could figure out how to count these chapters as such; so many interpret this number 84,000 as a figurative language to exemplify complexity of the Tipitaka. Scholars have categorized the Tipitaka into chapters and subchapters as follows:
The Contents and Structure of the Pali Canon and its Commentaries
THE PALI CANON
There are two sets of abbreviations of the names of Pali texts: the, now standard, Critical Pali Dictionary system, and the obsolescent Pali Text Society Dictionary system. These are given in brackets, below, with the CPD abbreviation first when the two differ.
(Vin): 'Basket of (monastic) Discipline'; PTS edition in 5 volumes (PTS translation: Book of the Discipline): monastic code (pâ.timokkha) for monks and for nuns, contained in the Suttavibha.nga, together with a commentary on that; the Khandhaka, dealing with the regulation of communal life, which is contained in the Mahâvagga and Cûlavagga. The Mahâvagga also contains some material on the life of the Buddha, etc.; the Parivâra, which is an abstract of the whole of the Vinaya Pi.taka, in dialogue form.
References are to volume and page number, eg. Vin III 59. Note that:
- Vin I and II (Mahâvagga and Cûlavagga) are translated as The Book of the Discipline vols IV and V.
- Vin III, IV (Suttavibha.nga) are translated as The Book of the Discipline vols I, II and III.
Also note that the translation, when it gives the Pali page number in the midst of the translation, gives it at the end of that page: eg  means p.1 ends here. In all other translations, it indicates where a page of the original starts.
'Basket of Discourses':
- Digha Nikaya (DN or D): 'Long Collection' of 34 Suttas; PTS edition in 3 volumes; PTS translation: Dialogues of the Buddha. References are usually given to the volume and page number of the PTS Pali text, e.g. DN III 33. To find this in translation, look at Dialogues of the Buddha vol. III, then find the section corresponding to p33 of the Pali by looking for  in the body of the text, which indicates where the translation of p33 starts. Some authors may simply refer to the Sutta number, eg. Dîgha no.12; but as the Suttas are quite long in this collection, this is not a very exact reference.
- Majjhima Nikaya (MN or M): 'Middle Length Collection' of 150 Suttas; PTS edition in 3 volumes'; PTS translation: Middle Length Sayings. The PTS translation volumes correspond to the first, second and third set of 50 Suttas, though the PTS Pali version groups them into 1-76, 77-100 and 101-150. Consequently vol. I of the text is translated in vol. I (for pp1-338 of text) and part of vol. II (for pp339-524) in the translation. References are sometimes made to the Sutta number, but it is more usual to refer to vol. and page number of the PTS Pali text, e.g. MN I 350, which can be found in vol.II of the translation: vol. no. and page no. of the Pali is given at top of the page, and the Pali page number is also included in the text of the translation: .
- Samyutta Nikaya (SN or S): 'Connected Collection' of 7,762 Suttas, grouped in 56 sections (sa.myuttas) according to subject matter; PTS edition in 5 volumes; PTS translation: The Book of Kindred Sayings. References are usually to volume and page number of the Pali text (e.g. SN III 79). These are given in the translation at the top of the left hand page, but exact Pali page-breaks are not indicated within the text of the translation. References are also given to section and Sutta number- which as the Suttas in this collection are each fairly short, is a reasonably exact way of giving a reference (though Sutta numbers differ in different editions). For these types of reference, see top of right hand page of translation (though this does not give the vol. number). An example: S.II.XV.I. 2. For this, look at Kindred Sayings vol. II, then look at contents page for 'chapter' (sa.myutta) XV, section I, then go to this part of the translation till 2 is found.
- Anguttara Nikaya(AN or A): 'Single-item Upwards Collection' of 9,550 Suttas, grouped according to the number of items dealt with in the Suttas, from one to eleven; PTS edition 5 volumes; PTS translation: The Book of Gradual Sayings. References are usually to volume and page number of the Pali text (e.g. AN IV 93). These are given in the translation at the top of the left hand page, but exact Pali page-breaks are not indicated within the text of the translation. (except in volume V). References are also given to the sutta number, eg. A.VI.VI.63: this can be found in the sixes (thus in Gradual Sayings vol.III- look at contents to find chapter VI of the sixes, then locate VI.VI.63 by looking at the top of the right hand page, and then down to where 63 starts.
- Khuddaka Nikaya: 'Collection of Little Texts': 15 separate miscellaneous texts, many in verse form, which contain both some of the earliest and latest material in the Canon:
- Khuddakapatha (Khp or Kh): 'Little readings': a short collection of texts for recitation; PTS edition in one volume, with its commentary; PTS translation: The Minor Readings. Reference usually by Sutta number and verse number.
- Dhammapada (Dhp or Dh): 'Verses on Dhamma', a popular collection of 423 pithy verses & associated stories, of a largely ethical nature; PTS edition in one volume; PTS translation available 1997. Reference by verse number.
- Udana (Ud): 'Verses of Uplift': 80 short Suttas based on inspired verses; PTS edition in one volume; PTS translation Verses of Uplift. Reference to page number of Pali text (e.g. Ud 54), or chapter and Sutta number.
- Itivuttaka (It): 'As It Was Said': 112 short Suttas; PTS edition in one volume; PTS translation: As it Was Said. Reference to page number of Pali text (e.g. It 12), or chapter and Sutta number.
- Suttanipata (Sn): 'Group of Discourses': a collection of 71 verse Suttas, including what some see as very early material, such as the A.t.thakavagga; PTS edition in one volume; PTS translation: Group of Discourses II and (paperback) The Rhinoceros Horn. References to verse number, or chapter, Sutta and verse number.
- Vimanavatthu (Vv): 'Stories of the Mansions', on heavenly rebirths; PTS edition in one volume, with the following; most recent PTS translation: Stories of the Mansions. Reference to chapter, Sutta and verse number.
- Petavatthu (Pv): 'Stories of the Departed': on ghostly rebirths; PTS edition in one volume, with last item; most recent PTS translation: Stories of the Departed. Reference to chapter, Sutta and verse number.
- Theragatha (Th or Thag): 'Elders' Verses', telling how a number of early monks attained enlightenment; PTS edition in one volume; PTS translations: Elders' Verses and Psalms of the Brethren. Reference to verse number.
- Therigatha (Thî or Thig): 'Elders' Verses': , telling how a number of early nuns attained enlightenment; PTS edition in one volume; PTS translations: Elders' Verses and Psalms of the Sisters, both in Poems of Early Buddhist Nuns. Reference to verse number.
- Jataka: a collection of 547 'Birth Stories' dealing with previous lives of the Buddha, with the aim of illustrating points in morality. The full stories are told in the commentary (JA), based on the verses and small sections of prose (J), which are canonical: PTS edition of text and commentary in 6 volumes; PTS translation of text and commentary: Stories of the Buddha's Former Births, with Story of Gotama Buddha giving the Buddha's life, from Vol.I of the commentary. Reference to volume and page number of Pali text, or to story number.
- Niddesa: Mahâ-Niddesa (NiddI or Nd1) and Culla-Niddesa (NiddII or Nd2): 'Exposition', in the form of a (canonical) commentary on part of the Suttanipâta; PTS edition in 3 volumes; no PTS translation available. Reference to page number of Pali text.
- Patisambhidamagga (Pa.tis or Ps): 'The Path of Discrimination', an Abhidhamma-style analysis of certain points of doctrine and practice; PTS edition in 2 volumes; PTS translation: The Path of Discrimination. Reference to volume and page number of Pali text.
- Apadana (Ap): 'Stories' on past lives of monks and nuns whose verses are given in the Theragâthâ and Therîgâthâ; PTS edition in 2 volumes; PTS translation of part of this text available 1997.
- Buddhavamsa (Bv): 'Chronicle of the Buddhas', on 24 previous Buddhas; PTS edition in one volume, with the next item; PTS translation: The Chronicle of the Buddhas. Reference by section and verse number.
- Cariyapitaka (Cp): 'The Basket of Conduct', on the conduct of Gotama in previous lives, building up the 'perfections' of a Bodhisatta; PTS edition in one volume, with the last item; PTS translation: The Basket of Conduct. Reference by section and verse number.
- Nettipakarana (The Guide): Nettipakarana is a guide to help those who already understand the teaching present it to others. The Netti methods were taught by the Buddha's disciple Kaccana (also Katyayana or Kaccayana). The Nettipakarana is divided into 1.Sangahavāra: collection of the contents; 2.Vibhāgavāra: the section which gives a systematic treatment in classified tables.
- Petakopadesa : The book was composed by the Buddha's disciple Kaccana (or Kaccayana). Scholars do not take this literally, though the translator mentions that the methods may go back to him. Scholars tend to give dates around the beginning of the common era.
- Milindapanha ("Questions of Milinda") : It purports to record a dialogue in which the Indo-Greek king Menander I (Pali Milinda) of Bactria, who reigned in the 2nd century BCE, poses questions on Buddhism to the sage Nāgasena.
'Basket of Further Dhamma': fine-grained analysis of experience, which seeks to systematise Sutta teachings, expressing them in psychologically and philosophically exact language:
- Dhammasangani (Dhs): 'Ennumeration of Dhammas': outline of the Theravâda dhamma list, with definitions of each, etc.; PTS edition in one volume; PTS translation: Buddhist Psychological Ethics. Reference by page number of Pali text, or discussion-item number.
- Vibhanga (Vibh or Vbh): '(The Book of) Analysis', dealing with various dhammas and groups of dhammas; PTS edition in one volume; PTS translation (of the Burmese edition): The Book of Analysis. Reference by page number of Pali text.
- Dhatukatha (Dhâtuk or Dhtk), discussing verious types of 'elements': PTS edition in one volume, with commentary; PTS translation: Discourse on Elements. Reference by page number of Pali text.
- Puggalapannatti (Pp or Pug): 'Concept of Persons', on various ways of classifying types of people; PTS edition in one volume, with its commentary; PTS translation: A Designation of Human Types. Reference by page number of Pali text, or chapter and section number.
- Kathavatthu (Kv or Kvu): 'Book of Discourses', detailing debates on various points of doctrine, with non-acceptable positions later being attributed, by the commentary, to non-Theravâdin schools; PTS edition in one volume; PTS translation; Points of Controversy. Reference by page number of Pali text, or chapter and section number.
- Yamaka (Yam): (Book of) Pairs': a book designed to test a student's grasp of Abhidhamma thinking; PTS edition in 2 volumes; no PTS translation available. Reference by page number of Pali text.
- Patthana (Pa.t.th or Pt): 'Conditional Relations': which goes into great detail on the various kinds of relationships existing between dhammas; PTS edition (incomplete): Tika-pa.t.thâna (Tikap or Tkp) in three volumes, with its commentary and Duka-pa.t.thâna (Dukap or Dkp), in one volume; the (incomplete) PTS translation corresponding to the first (it is actually of the Burmese edition) is Conditional Relations, the second has no PTS translation. Reference by page number of Pali text.