Declension.—Bihari has a stronger sense of gender than the other languages of the Eastern Group. In the modern language the distinction is in the main confined no animate beings, but in the older poetry the system of grammatical, as distinct from sexual, gender is in full swing. Except in the case of the interrogative pronoun, there is no neuter gender—words which in Skr. and Pr. were neuter being generally, but not always, treated as masculine. The plural can everywhere be formed by the addition of some noun of multitude to the singular, and this is the universal rule in Mth., but in Mg. and Bh. it is generally made by adding n or (in Bh.) nh or ni to the singular, before all of which a final vowel is shortened. Thus ghōṛā, a horse, ghōṛan, horses.
As for cases, the Apabhraṁśa locative—hi (-hi) and the ablative -hu (see [Prakrit]) terminations have survived in poetry, proverbs and the like, and each of them can now be used for any oblique case; but in ordinary language and in literature -hi and -hi have become contracted to ẻ and ē, the former of which is employed for the instrumental and the latter for the locative case. Thus, ghar, house; gharẻ, by a house; gharē, in a house. The old termination -hu has also survived in sporadic instances, under the form ỏ, with an ablative sense. Cases are, however, usually formed, as elsewhere, by suffixing postpositions to a general oblique case (see [Indo-Aryan Languages]). The oblique case in Bihari is generally the same as the nominative, but nouns ending in n, b, l or r, and some others, form it by adding ā (a relic of the old Mg. Pr. genitive in āha). Thus, maral, the act of striking, obl. mảralā (Mg. Pr. mảri-allāha). Another set of verbal nouns forms the oblique case in ai, e or ả, thus, Bh. mār, the ace of striking, mārē-la, for striking, to strike. In Mg. every noun ending in a consonant may have its oblique form in e; thus, ghar, a house, ghar-ke or ghare-ke, of a house. The ai- or e- termination is another relic of the Apabhrarhsa -hi, and the ả is a survival of the Ap. -hu.
The usual genitive postposition is k, which has become a suffix, and now forms part of the word to which it is attached, a final preceding vowel being frequently shortened. Thus, ghōṛā, gen. ghōṛāk. Other genitive postpositions are ke, kar and kēr. These, and all other postpositions, are still separate words, and have not yet become suffixes. The more common postpositions are[1] Acc.-Dat. ke; Instr.-Abl. så, sē; Loc. må., mē. The genitive does not change to agree with the gender of the governing noun, as in Hindostani, but in Bh. (not in Mth. or Mg.), when the governing noun is not in the nominative singular, the genitive postposition takes the oblique form kā; thus, rājā-ke mandir, the palace of the king; but rājā-kā mandir-mē, in the palace of the king. In Mth. and Mg. pronouns have a similar oblique genitive in ā. There is no case of the agent, as in Hindostani; the subject of all tenses of all verbs being always in the nominative case.
Every noun can have three forms, a short, a long and a redundant. The short form is sometimes weak and sometimes strong. Occasionally both weak and strong forms occur for the same word; thus, short weak, ghōṛ; short strong, ghōṛā; long, ghoṛawā; redundant, ghoṛauwā. This superfluity of forms is due to the existence of the pleonastic suffix -ka- in the Prakrit stage of the language (see [Prakrit]). In that stage the k of the suffix was already elided, so that we have the stages:—Skr. ghōṭa-ka-s, Pr. ghōḍ-a-u, B. ghōṛā (by contraction) or ghoṛa-wā (with insertion of a euphonic w). The redundant form is a result of the reduplication of the suffix, which was allowed in Pr. Thus. Skr. *ghōṭa-ka-ka-s, Pr. ghōḍa-a-a-u, B. ghoṛauwā (contracted from ghoṛa-wa-wa-a). The long and redundant forms are mainly used in conversation. They are familiar and often contemptuous. Sometimes they give a definite force to the word, as ghoṛawā, the horse. In the feminine they are much used to form diminutives.
As in other languages of the Eastern Group, the singulars of the personal pronouns have fallen into disuse. The plurals are used politely for the singulars, and new forms are made from these old plurals, to make new plurals. The old singulars survive in poetry and in the speech of villagers, but even here the nominative has disappeared and new nominatives have been formed from the oblique bases. All the pronouns have numerous optional forms. As a specimen of pronominal declension, we may give the most common forms of the first personal pronoun.
| Maithilī. | Magahī. | Bhojpurī. | |
| Sing. Nom. | ham | ham | ham |
| Gen. | hamār | hamār | hamār |
| Obl. | hamarā | hamarā | hamarā |
| Plur. Nom. | hamarā sabh | hamaranī | hamanī-kā |
| Gen. | hamarā sabhak | hamaranī-ke | hamanī-ke |
| Obl. | hamarā sabh | hamaranī | hama nī |
The important point to note in the above is that the oblique form singular is formed from the genitive. It is the oblique form of that case which is also used when agreeing with another noun in an oblique case. Thus, hamār ghar, my house; hamarā ghar-mẽ, in my house; hamarā-kē, to me. In Mth. the nominative plural is also the oblique form of the genitive singular, and in Bh. and Mg. it is the oblique form of the genitive plural. In Bengali the nominative plural of nouns substantive is formed in the same way from the genitive singular (see [Bengali]). The usual forms of the pronouns are ham, I; tṍ, tṹ, thou; Mth. apanahī, Bh. raurā, Your Honour; ī, this; ō, that, he; jē, who; sē, he; kē, who? Mth. kī, Mg., Bh. kā, what? keo, keu, any one; Mth. kicchu, Mg. kuchu, Bh. kachu, anything. The oblique forms of these vary greatly, and must be learned from the grammars.
Conjugation in Maithili and Magahi.—It is in the conjugation of the verb that the amazing complexity of the Mth. and Mg. grammars appears. The conjugation of the Bhojpuri verb is quite simple, and will be treated separately. In all three dialects the verb makes little or no distinction of number, but instead there is a distinction between non-honorific and honorific forms. In Mth. and Mg. this distinction applies not only to the subject but also to the object, so that for each person there are, in the first place, four groups of forms, viz.:—
| I. | Subject non-honorific, object non-honorific. |
| II. | Subject honorific, object non-honorific. |
| III. | Subject non-honorific, object honorific. |
| IV. | Subject honorific, object honorific. |
| Object: non-honorific | Object: honorific | |||||||
| Person. | Short Form | Long Form | Redundant Form. | Group III. (Subject: non- honorific) | Group IV. (Subject: honorific) | |||
| Group I. (Subject: non- honorific) | Group II. (Subject: honorific) | Group I. (Subject: non- honorific) | Group II. (Subject: honorific) | Group I. (Subject: non- honorific) | Group II. (Subject: honorific) | |||
| 1 | mảralī or mảralakū | mảraliai Or (with object in 2nd person) mảraliau | mảraliaik Or (with object in 2nd person) maraliauk | mảraliainhi | ||||
| 2 | mảralẽ | Same as 1st person. | mảralảh | Same as 1st person, but no forms for object in 2nd person. | mảralahảk | Same as 1st person, but no forms for object in 2nd person. | mảralukūnhi | Same as 1st person. |
| 3 | mảralak | mảralunhi | mảralakai Or (with object in 2nd person) mảralakau | Wanting | mảralakaik Or (with object in 2nd person) mảralakauk | Wanting | mảralakainhi | mảralathīnhi |