One notable feature of the agglutinative nominal system of Classical Sanskrit is the very common use of nominal compounds (samāsa), which may be huge (10+ or even 30+ words) and are generative. Nominal compounds occur with various structures, but morphologically speaking they are essentially the same: each noun (or adjective) is in its (weak) stem form, with only the final element receiving case inflection.
Contents
Avyayībhāva
The first member of this type of nominal compound is an indeclinable, to which another word is added so that the new compound also becomes indeclinable (i.e., avyaya). Examples: yathā+śakti, upa+kṛṣṇam (near kṛṣṇa), etc. In avyayībhāva compounds, first member has primacy (pūrva-pada-pradhāna), i.e., the whole compound behaves like an indeclinable due to the nature of the first part which is indeclinable.
Tatpuruṣa (determinative)
Unlike the avyayībhāva compounds, in Tatpuruṣa compounds the second member has primacy (uttara-pada-pradhāna). There are many tatpuruṣas (one for each of the nominal cases, and a few others besides). In a tatpuruṣa, the first component is in a case relationship with another. For example, a doghouse is a dative compound, a house for a dog. It would be called a "caturtitatpuruṣa" (caturti refers to the fourth case, that is, the dative). Incidentally, the word "tatpuruṣa" is itself a tatpuruṣa (meaning a "that-man", in the sense of "a man of that (person)", meaning someone's agent), while "caturtitatpuruṣa" is a Karmadhāraya, being both dative, and a tatpuruṣa.
An easy way to understand it is to look at English examples of tatpuruṣas: "battlefield", where there is a genitive relationship between "field" and "battle", "a field of battle"; other examples include instrumental relationships ("thunderstruck") and locative relationships ("town-dwelling"). All these normal Tatpuruṣa compounds are called vyadhikarana Tatpuruṣa, because the case ending should depend upon the second member because semantically the second member has primacy, but actually the case ending depends upon the first member. Literally, vyadhikarana means opposite or different case ending. But when the case ending of both members of a Tatpuruṣa compound are similar then it is called a Karmadhāraya Tatpuruṣa compound, or simply a Karmadhāraya compound.
Dvigu
Dvigu is a subtype of tatpuruṣa in which the modifying member is a number. Dvigu itself is a compound : dvau+gāvau.
Karmadhāraya (descriptive)
It is a variety of Tatpuruṣa as shown above, but treated separately. The relation of the first member to the last is appositional, attributive or adverbial, e. g. ulūka-yātu (owl+demon) is a demon in the shape of an owl.
Madhyama-pada-lopī-samāsa
It is that variety of Karmadhāraya tatpuruṣa compound in which the middle part vanishes. E.g., devapūjakaḥ+brāhamaṇaḥ = devabrāhamaṇaḥ; Śrīyukta+Rāmaḥ = Śrīrāmaḥ
Nañ-samāsa
Example: na + brāhamaṇa = abrāhamaṇa, in which 'n' vanishes and only the 'a' of 'na' remains. But with words beginning with a vowel this 'a' becomes 'an': na+aśva > (na > a > an) anaśva.
Upapada-samāsa
A variety of Tatpuruṣa compound in which nouns make unions with verbs. These compounds can be recognized by the fact that the second Pada contains a (possibly transformed) verbal root (dhātu): kumbham + kṛ = kumbhakāra [potter, lit. one who makes pots]; śāstram + jñā = śāstrajña [learned person, one who knows treatises]; jalam + dā = jalada [cloud, one who gives water].
Dvandva (co-ordinative)
These consist of two or more noun stems, connected in sense with 'and' (copulative or coordinative). There are mainly two kinds of द्वन्द्व (dvandva pair) constructions in Sanskrit:
Itaretara dvandva
The result of इतरेतर द्वन्द्व (itaretara dvandva enumerative dvanda) is an enumerative word, the meaning of which refers to all its constituent members. The resultant compound word is in the dual or plural number and takes the gender of the final member in the compound construction. For example:
Samāhāra dvandva
Words may be organised in a compound to form a metonym, and sometimes the words may comprise all the constituent parts of the whole. The resultant compound word exhibits समाहार द्वन्द्व (samāhāra dvandva collective dvandva), and is always neuter and in the singular number.
According to some grammarians, there is a third kind of dvandva, called एकशेष द्वन्द्व ekashesha dvandva one-(stem)-remains dvandva, where only one stem remains in the compound of multiple words: this exhibits "true" metonymy.
Bahuvrīhi (possessive)
Bahuvrīhi, or "much-rice", denotes a rich person—one who has much rice. Bahuvrīhi compounds refer (by example) to a compound noun with no head—a compound noun that refers to a thing which is itself not part of the compound. For example, "low-life" and "block-head" are bahuvrīhi compounds, since a low-life is not a kind of life, and a block-head is not a kind of head. (And a much-rice is not a kind of rice.) Compare with more common, headed, compound nouns like "fly-ball" (a kind of ball) or "alley cat" (a kind of cat). Bahurvrīhis can often be translated by "possessing..." or "-ed"; for example, "possessing much rice", or "much-riced".
In simple terms, it is a compound which is an adjective for a third word which is not a part of the compound.
Aluk-samāsa
Case endings do not vanish, e.g., ātmane+ padam = ātmanepadam.
Āmreḍita (iterative)
A compound consisting of the same word repeated, but with the first occurrence being accented. Amreditas are used to express repetitiveness; for example, from dív (day) we obtain divé-dive (day after day, daily) and from devá (god) we obtain deváṃ-devam or devó-devas (god after god).