g. The numbers 21–29 are made like those for 31–39; the numbers 41–49, 51–59, 71–79, and 91–99 are made like those for 61–69.
h. The forms made with dvā and trayas are more usual than those with dvi and tri, which are hardly to be quoted from the older literature (V. and Br.). The forms made with aṣṭā (instead of aṣṭa) are alone found in the older literature (483), and are usual in the later.
477. The above are the normal expressions for the odd numbers. But equivalent substitutes for them are also variously made. Thus:
a. By use of the adjectives ūna deficient and adhika redundant, in composition with lesser numbers which are to be subtracted or added, and either independently qualifying or (more usually) in composition with larger numbers which are to be increased or diminished by the others: thus, tryūnaṣaṣṭiḥ sixty deficient by three (i. e. 57); aṣṭādhikanavatiḥ ninety increased by eight (i. e. 98); ekādhikaṁ çatam a hundred increased by one (i. e. 101); pañconaṁ çatam 100 less 5 (i. e. 95). For the nines, especially, such substitutes as ekonaviṅçatiḥ 20 less 1, or 19, are not uncommon; and later the eka 1 is left off, and ūnaviṅçati etc. have the same value.
b. A case-form of a smaller number, generally éka one is connected by ná not with a larger number from which it is to be deducted: thus, ékayā ná triṅçát (ÇB. PB. KB.) not thirty by one (29); dvābhyāṁ ná ’çītím (ÇB.) not eighty by two (78); pañcábhir ná catvā́ri çatā́ni (ÇB.) not four hundred by five (395); ékasmān ná pañcāçát (in ordinal) 49 (TS.); ékasyāi (abl. fem. : 307 h) ná pañcāçát 49 (TS.); most often, ékān (i. e. ékāt, irregular abl. for ékasmāt) ná viṅçatíḥ 19; ékān ná çatám 99. This last form is admitted also in the later language; the others are found in the Brāhmaṇas.
c. Instances of multiplication by a prefixed number are occasionally met with: thus, triṣaptá thrice seven; triṇavá thrice nine; tridaçá thrice ten.
d. Of course, the numbers to be added together may be expressed by independent words, with connecting and: thus, náva ca navatíç ca, or náva navatíç ca ninety and nine; dvāú ca viṅçatíç ca two and twenty. But the connective is also (at least, in the older language) not seldom omitted: thus, navatír náva 99; triṅçátaṁ trī́n 33; açītír aṣṭāú 88.
478. The same methods are also variously used for forming the odd numbers above 100. Thus:
a. The added number is prefixed to the other, and takes the accent: for example, ékaçatam 101; aṣṭāçatam 108; triṅçácchatam 130; aṣṭāviṅçatiçatam 128; cátuḥsahasram (RV.: unless the accent is wrong) 1004; açītisahasram 1080.