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One notable feature of the agglutinative nominal system of Classical Sanskrit is the very common use of nominal compounds (sam?sa), 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.
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: yath?+?akti ("per power"; as much as possible), upa+kam (near ka), etc. In avyay?bh?va compounds, the first member has primacy (p?rva-pada-pradh?na), i.e., the whole compound behaves like an indeclinable due to the nature of the first part which is indeclinable.
Unlike the avyay?bh?va compounds, in Tatpuru?a compounds the second member has primacy (uttara-pada-pradh?na). There are many types of tatpuru?a (one for each of the nominal cases, and a few others besides). In a tatpuru?a, the first component is in a case relationship with another. For example, "doghouse" is a dative compound, a house for a dog. It would be called a caturth?tatpuru?a refers to the fourth case, that is, the dative). Incidentally, the word "tatpuru?a" is itself a tatpuru?a (meaning a "that-man", in the sense of "that person's man", meaning someone's agent), while "caturth?tatpuru?a" is a karmadh?raya, being both dative and a tatpuru?a.
An easy way to understand it is to look at English examples of tatpuru?as: "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 Tatpuru?a compounds are called vyadhikarana-tatpuru?a, 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 tatpuru?a compound are similar, then it is called a karmadh?raya tatpuru?a compound, or simply a karmadh?raya compound.
Dvigu is a subtype of tatpuru?a in which the modifying member is a number. Dvigu (lit., "[a] two-cow [person]"; i.e., one who has two cows) itself is a compound : dvau+g?vau.
It is a variety of tatpuru?a as shown above, but treated separately. The relation of the first member to the last is appositional, attributive or adverbial, e. g. ul?ka-y?tu (owl+demon) is a demon in the shape of an owl.
It is that variety of Karmadh?raya tatpuru?a compound in which the middle part is implied but not present for brevity. E.g., deva-br?hma?a?, lit. "god-Brahmin", concatenated from deva-p?jaka? br?hma?a? "god-worshipping Brahmin".
Example: na + br?hma?a = a-br?hma?a, in which 'na' when placed in an initial position becomes 'a-' (or an- before a word starting with a vowel). While useful in classification, this is etymologically incorrect as the 'a-' negation has not originated from na.
A variety of tatpuru?a compound in which nouns make unions with verbs. These compounds can be recognized by the fact that the second part contains a (possibly transformed) verbal root (dh?tu): kumbham + k? = kumbhak?ra [potter, lit. pot-maker]; stram + jñ? = strajña [learned person, one who knows treatises]; jalam + d? = jalada [one that gives water; cloud].
These consist of two or more noun stems, connected in sense with 'and' (copulative or coordinative). There are mainly two kinds of (dvandva pair) constructions in Sanskrit:
The result of (itaretara dvandva "enumerative dvandva") 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:
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 (sam?h?ra dvandva collective dvandva), and is always neuter and in the singular number.
According to some grammarians, there is a third kind of dvandva, called ekashesha dvandva one-(stem)-remains dvandva, where only one stem remains in the compound of multiple words: this exhibits "true" metonymy.
Bahuvr?hi, or "much-rice", denotes a rich person--one who has much rice. Bahuvr?hi 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 bahuvr?hi 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). Bahurvr?his 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.
Case endings do not vanish, e.g., ?tmane+ padam = ?tmanepadam.
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 devá?-devam or devó-devas (god after god).
A compound with 16 words and 44 syllables from the Bhusundi Ramayana: ?--?-?--?-?--?---?-?-?-?- (IAST kamal?-kuca-ku?kuma-pinjar?k?ta-vak?a?-sthala-vir?jita-mah?-kaustubha-ma?i-mar?ci-m?l?-nir?k?ta-tri-bhuvana-timira).
A compound with 35 words and 86 syllables from the Virudavali of Rambhadracharya: ?---?--?-?-?----?------?-----?-?----- (IAST skhya-yoga-ny?ya-vai?e?ika-p?rva-m?ms?-ved?nta-n?rada-?ilya-bhakti-s?tra-g?t?-v?lm?k?ya-r?m?ya?a-bh?gavat?di-siddh?nta-bodha-pura?-sara-samadhik?te?a-tulas?-d?sa-s?hitya-sauhitya-sv?dhy?ya-pravacana-vy?khy?na-parama-prav?).