Dvandva

A dvandva (Sanskrit द्वन्द्व dvandva 'pair') or copulative or coordinative compound refers to two or more objects that could be connected in sense by the conjunction 'and'. Dvandvas are common in some languages such as Sanskrit where the term originates, as well as Chinese, Japanese, and some Modern Indic languages such as Hindi and Urdu, but less common in English (the term is not often found in English dictionaries). Examples include Sanskrit mātāpitarau (मातापितरौ) for 'mother and father'; Chinese shānchuān and Japanese yamakawa (山川) for 'mountains and rivers'; and English singer-songwriter, twenty-two, and whiskey-soda.

Sanskrit
There are two or three kinds of dvandva compounds in Sanskrit, depending on classification.

Itaretara dvandva
The first, and most common kind, the itaretara dvandva, is an enumerative compound word, the meaning of which refers to all its constituent members. The resultant compound word is in the dual or plural number, depending on the total number of described individuals. It takes the gender of the final member in the compound construction. Examples:
 * rāma-lakşmaņau (dual) 'Rama and Lakshmana'
 * हरिहरौ hari-harau (dual) 'Hari and Hara'
 * आचार्यशिष्यौ ācārya-śiṣyau (dual) 'teacher and student'
 * rāma-lakşmaņa-bharata-śatrughnāh (plural) 'Rama, Lakshmana, Bharata and Satrughna'
 * नराश्वरथदन्तिनः nar-āśva-ratha-dantinaḥ (plural) 'men, horses, chariots, and elephants'
 * देवमनुष्याः deva-manuṣyāḥ (plural) 'gods and humans'

Itaretaras formed from two kinship terms behave differently, in that the first word is not in the compound form but in the nominative (singular).
 * मातापितरौ mātā-pitarau 'mother and father'

Samāhāra dvandva
The second, rarer kind is called samāhāra dvandva and is a collective compound word, the meaning of which refers to the collection of its constituent members. The resultant compound word is in the singular number and is always neuter in gender. Examples:
 * pāņipādam 'limbs', literally 'hands and feet', from pāņi 'hand' and pāda 'foot'

Ekaśeşa dvandva
According to some grammarians, there is a third kind of dvandva, called ekaśeşa dvandva or residual compound. It is formed like a itaretara, but the first constituent is omitted. The remaining final constituent still takes the dual (or plural) number. According to other grammarians, however, the ekaśeşa is not properly a compound at all. An example:
 * pitarau 'parents', from mātā 'mother' + pitā 'father'