Numbers

Numbers have two forms

• cardinal, which indicate the quantity of something
  • sixty-seven dollars
• ordinal, which indicate the order of things
  • the sixty-seventh dollar

Numbers are mostly adjectives. Sometimes they are used as nouns (most often mille and primus).

No source has said this, but I'm assuming that for compounds, each part does its own thing in declination (like the quid and dam in quidam).

Cardinal

Most cardinals are undeclined.

unus

unus is declined like a 1/2dec -ius adjective.

	M	F	N	M PL	F PL	N PL
nom	unus	una	unum	uni	unae	una
acc	unum	unam	unum	unos	unas	una
gen	unius	unius	unius	uni	unae	uni
dat	uni	uni	uni	unis	unis	unis
abl	uno	una	uno	unis	unis	unis

The plural is necessary because:

• unus also means same or only
• to agree with plural only nouns of a singular meaning
  • una balena? one bathhouse?

duo

duo is PL only and irregular.

	M PL	F PL	N PL
nom	duo	duae	duo
acc	duos | duo	duas	duo
gen	duorum	duarum	duorum
dat	duobus	duabus	duobus
abl	duobus	duabus	duobus

tres

tres is PL only and declined like a 3rd declension i-stem adjective. it's two-termination.

	M/F PL	N PL
nom	tres	tria
acc	tres | tris	tria
gen	trium	trium
dat	tribus	tribus
abl	tribus	tribus

hundreds

200, 300, 400, 500, 600, 700, 800, 900, are declined like first declension plural only adjectives.

mille

mille is singular only. The plural meaning is supplied by the NT PL noun mīlia, mīlium, plus the genitive of whatever thing you're describing.

• mille homines
• mille hominum (with mille as a noun)
• duo milia hominum
• cum duobus milibus hominum (note how octo is a numerical adjective that describes milibus - we have come full circle)

milia, milium is also found with a double L (millia, millium)

n > 10 and n % 10 in (8, 9)

?? (I copy and pasted this)

The forms octōdecim, novendecim are rare, duodēvīgintī (two from twenty), ūndēvīgintī (one from twenty), being used instead. So 28, 29; 38, 39; etc. may be expressed either by the subtraction of two and one or by the addition of eight and nine respectively.

Ordinal

Everything is declined like first declension adjectives. Example:

• secundus, secunda, secundum
• alter, altera, alterum

Ordinals ending in -<ēnsimus> are often written without <n>

• vīcēnsimus → vīcēsimus

Reference Sheet

secundus only means 'second' in the sense of 'following'. The adjective alter, altera, alterum meaning 'other [of two]' was more frequently used in many instances where English would use 'second'.

The conjunction et between (cardinal only?) numerals can be omitted: vīgintī ūnus, centum ūnus. Et is not used when there are more than two words in a compound numeral: centum trīgintā quattuor. The word order in the numerals from 21 to 99 may be inverted: ūnus et vīgintī.

decimal	cardinal	ordinal	roman numerals
1	ūnus	prīmus	I
2	duo	secundus; alter	II
3	trēs	tertius	III
4	quattuor	quārtus	IIII or IV
5	quīnque	quīntus	V
6	sex	sextus	VI
7	septem	septimus	VII
8	octō	octāvus	VIII
9	novem	nōnus	VIIII or IX
10	decem	decimus	X
11	ūndecim	ūndecimus	XI
12	duodecim	duodecimus	XII
13	tredecim	tertius decimus	XIII
14	quattuordecim	quārtus decimus	XIIII or XIV
15	quīndecim	quīntus decimus	XV
16	sēdecim	sextus decimus	XVI
17	septendecim	septimus decimus	XVII
18	duodēvīgintī; octōdecim	duodēvīcēnsimus; octāvus decimus	XVIII
19	ūndēvīgintī; novendecim	ūndēvīcēnsimus; nōnus decimus	XVIIII or XIX
20	vīgintī	vīcēnsimus; vīgēnsimus	XX
21	vīgintī (et) ūnus; ūnus (et) vīgintī	vīcēnsimus prīmus	XXI
30	trīgintā	trīcēnsimus	XXX
40	quadrāgintā	quadrāgēnsimus	XXXX or XL
50	quīnquāgintā	quīnquāgēnsimus	↓ or L
60	sexāgintā	sexāgēnsimus	LX
70	septuāgintā	septuāgēnsimus	LXX
80	octōgintā	octōgēnsimus	LXXX
90	nōnāgintā	nōnāgēnsimus	LXXXX or XC
100	centum	centēnsimus	C
101	centum (et) ūnus	centēnsimus prīmus	CI
200	ducentī	ducentēnsimus	CC
300	trecentī	trecentēnsimus	CCC
400	quadringentī	quadringentēnsimus	CCCC
500	quīngentī	quīngentēnsimus	D
600	sescentī	sescentēnsimus	DC
700	septingentī	septingentēnsimus	DCC
800	octingentī	octingentēnsimus	DCCC
900	nōngentī	nōngentēnsimus	DCCCC or Cↀ
1000	mīlle	mīllēnsimus	ↀ or M
5000	quīnque mīlia	quīnquiēns mīllēnsimus	IϽϽ
10,000	decem mīlia	deciēns mīllēnsimus	CCIϽϽ
100,000	centum mīlia	centiēns mīllēnsimus	CCCIϽϽϽ

references

https://dcc.dickinson.edu/grammar/latin/declension-cardinals-and-ordinals