The cardinal numbers are productively formed on the basis of fourteen free morphemes:

Free morphemes	Translation
ien	one
twa	two
trije	three
fjouwer	four
fiif	five
seis	six
sân	seven
acht	eight
njoggen	nine
tsien	ten
alve	eleven
tolve	twelve
hûndert	hundred
tûzen	thousand

and a few bound morphemes: -tich-ty, -en-and, -oen-on, -ard-ard, milj-mill-, bilj-bill-.

The suffix -tich (pronounced [təχ]) makes names for powers of ten. It is like English -ty (as in forty), German -zig (as in vierzigforty) and Dutch -tig (as in veertigforty) in that it is etymologically related to -tien, -ten, -zehn. The bound morphemes-oen-on and -ard-ard are used with milj-mill-, etc. to build internationalisms like miljoenmillion, miljardbillion and biljoenten to the power twelve.

Morphemes are combined by something that looks like compounding but with a different semantics: it is not intersective but is rather additive (sech(s)-tjin = 6+10) or multiplicative at other times (seis-hûndert = 6*100). The element -en- looks exactly like coordinating enand but it has a restricted, i.e. additive, semantics: twa-en-tritichtwo.and.thirtythirty two, hûndert(en)seishundred.(and).sixone hundred and six. The conjunction element en can be omitted in numbers above 100. For example, hûndertentsienone hundred and ten and hundertsien are both grammatical. In numbers below 100, the conjunction element is obligatory: ienentweintichtwenty-one vs *ientwintichtwenty-one. Another difference between these numbers is that above 100, the <e> in en is pronounced as [ɛ], below 100 it is pronounced as [ə].

The following table gives an impression of the basic pattern:

1	ien	12	tolve (tolf)	30	tritich
2	twa	13	trettjin	40	fjirtich
3	trije	14	fjirtjin	50	fyftich
4	fjouwer	15	fyftjin	60	sechtich
5	fiif	16	sechtjin	70	santich
6	seis	17	santjin	80	tachtich
7	sân	18	achttjin	90	njoggentich
8	acht	19	njoggentjin	100	hûndert
9	njoggen	20	tweintich	1000	tûzen
10	tsien	21	ienentweintich	1.000.000	miljoen
11	alve (âlf)	22	twaentweintich	1.000.000.000	miljard

The cardinal numbers are never inflected, except ienone in the expression de ienethe one (in contrast to de oarethe other).

Some of the vowels of the single numbers that undergo shortening or breaking display allomorphy among them as a result, when they are used as the left-hand member of a higher number. Twa[twa:]two may be shortened to [twa] if used attributively, for instance in twa boekentwo books. It has an allomorphtwein- or twin- in tweintich/twintichtwenty. For trijethree there is tret- in trettjinthirteen and tri- in tritichthirty; for fjouwerfour there is fjir- in fjirtjinfourteen and fjirtichforty; for fiif the vowel is shortened tofyf-/fif/ or even further rounded to /fyf-/ in fyftjinfifteen and fyftichfifty; for seissix there is sech(s)- in sech(s)tjinsixteen and sech(s)tichsixty. Sânseven is shortened to san-/sɔn-/ in santjinseventeen and santichseventy and for achteight there is tacht- in tachticheighty. Njoggen[njoɣən]nine may be heavily shortened in njoggentjin19 and njoggentich90 to [njon], or also with a centralizing diphthong to [njo.ən]. Frisian has a few more numbers with allomorphs than Dutch. For more information about shortening and breaking, see Allomorphy in Frisian: 'broken and 'shortened' forms.

The number ienone undergoes breaking when it becomes part of a larger number. So the number ienentritichone.and.thirtythirty one is pronounced as [jɪnn̩tritəx], also with a syllabic consonant [n]. Furthermore, tsienten was historically subject to breaking in the numbers trettjinthirteen, fjirtjinfourteen, fyftjinfifteen, sech(s)tjinsixteen, santjinseventeen, achttjineighteen and njoggentjinnineteen.

In cardinals between 12 and 20, the word order is low-high (five plus ten: fyftjinfifteen) and the semantics is additive. In the names of the units of 10, the order is [stem]-tich. If we assume that -tich means '10', the semantics is multiplicative: sech(s)-tich6*10sixty. Between 21 and 99, the structure is small-and-large and the semantics is additive: trije-en-sech(s)tich3+60sixty-three. In units of 100, 1000 and higher, the order is small before large again, but the semantics is multiplicative: trijehûndert3*100three hundred, seistûzen6*1000six thousand, fjouwerentritich-miljoen34*1000000thirty four million. Complex numbers larger than 100 are built from the building blocks just described: the number 363 is trijehûnderttrije-en-sechtich(3*100)+(3+60)three hundred-sixtythree.

The formation of cardinals can be schematized as follows (according to Booij (2010)):

• 13-19: no overt conjunction, lower number before higher number;
• 21-99: conjunction, lower number before higher number;
• > 100: optional conjunction before the last numeral, higher number before lower number.

Some numbers can be pronounced in more than one way. The number 1421 may be tûzen fjouwerhûndert ienentweintichthousand four.hundred one.and.twenty or preferably fjirtjinhûndert-ienentweintichfourteen.hundred-one.and.twenty. When the number is used in names of years, there is a third possibility, as hûnderthundred may be left implicit: fjirtjin ienentweintichfourteen one.and.twenty. One cannot use the otherwise well-formed expression tûzen fjouwerhûndert ienentweintich for denoting the year 1421.

In temporal expressions (phrases of time), the cardinals get the suffix -en:

A condition is that the cardinal should stand alone; it may not be followed by a noun:

In this case oereo'clock is expressed, and the cardinal does not get the suffix -en. In case of an elliptic construction, when the noun oere is omitted, the suffix -en is obligatorily added to the numeral.

A condition for the presence of the suffix is that the numeral should be preceded by one of the following prepositions: foarbefore, neiafter, tsjinagainst, bynear, om ... hinnearound and healweihalf past. In spoken Frisian, omaround of the circumfix om ... hinnearound can be left out, as in acht oere hinne stapten wy yn 'e autoaround eight o'clock we got into the car.

The preposition tuskenbetween may be used when the elliptic clocktimes are coordinated:

The construction om NUM-en en NUM-en, for instance in om trij-en en fjouwer-enaround three-SUFF and four-SUFFsomewhere between three and four o'clock is slightly idiomatic.

In Frisian we find a collective construction in the form of an Adposition Phrase (PP) with the preposition meiwith. This PP consists of a possessive pronoun and a numeral. To the numeral an ending -en is attached. There is a coreference relation between the possessive pronoun and the subject of the sentence, as in the following examples:

The suffix -en is usually dependent on the existence of the preposition. An independent phrase *ús fjouweren is ungrammatical. An exception is the first person plural subject pronoun wywe, which may be followed by a suffixed numeral, for instance in:

The suffix can also be attached to the quantifiers alleall, beideboth and in stikmannicha few, as in the sentence: wy geane mei ús allenwe go with us all-SUFFwe go all together. In the following quote we also see an added adjunct:

The adjunct fen kammeraten further characterizes the subject sethey. Another example of such an adjunct headed by the preposition fanof is mei ús trij-en fan boerenwith us three-SUFF of farmers, which means with the three of us, being farmers. This kind of adjunction seems to be disappearing in the present-day language, however.

The ending -en is the normal plural suffix that we also find in nouns. However, as Booij (2010:234-235) points out with respect to the comparable construction in Dutch, there is a problem here. In Frisian and Dutch, there is a regular distribution between the two available plural suffixes -en and -s. The suffix -en is attached to stressed syllables and -s to unstressed ones. According to this system, fjouwerfour, with a schwa in its second syllable, would regularly take the plural suffix -s. This is clear from an example in which fjouwer really acts as a noun:

Hence, it appears from this particular construction that -en is not the ordinary plural morpheme, but something else. This 'something else' makes sense if we analyze the construction as a case of ellipsis. It seems that something like PERSON has been omitted here. The ending -en, then, would be an instance of special morphology connected to ellipsis. This view makes the more sense because of the coreference relation with the subject, which might then be viewed as a kind of antecedent, although not in the standard way. This could also be an explanation of the fact that such pluralized numerals cannot act as a subject themselves, as Booij (2005a:12) also notes for Dutch:

The preposition that preferably combines with the possessive pronoun + numeral+-en is mei. The possessive pronoun is obligatory: *mei fjouweren. The phrase can not be expanded by an adjective:

Frisian also has a construction by + Numeral + -en which means in groups of [numeral] persons. For example:

The ending -en may also be found after the preposition fanof, in an adjunct after a noun denoting a set, as in in ploech fan fjouwerena group of four. Note that after these prepositions the possessive pronoun is lacking.

In Frisian, as well as in Dutch, we can find the following elliptic construction:

As can been seen in (11) and (12), apparently, something like the concept 'part' has been left out. Again, there is a suffix -en involved, and again it is attached to a number. Usually, the preposition yn is used as the head of the PP, although its counterpart út is not excluded:

Quite idiosyncratic is the idiom yn twaen falle, literally to fall in two-en, i.e. to get a baby.

The suffixed numeral fjouwer-enfour-SUFF has a special sense in that it can refer to the feet of a horse. The adverbial phrase út 'e fjouwer-enout the four-SUFF means at a gallop. Op fjouwer-en setteon four-SUFF set is fit a horseshoe. The phrase op fjouwer-en be-slein wêzeon four-SUFF PREF-hit bebeing shoed has an extra metaphorical meaning: know how to go about things.

Frisian has an idiomatic construction in N of Num, as shown in the examples below:

Of cannot be replaced by, for example, en or noch, so in N of Num is a fixed expression:

The two variable parts of the construction are the noun and the numeral. The noun is always morphologically singular, while it can be interpreted as plural, and cannot easily be modified (as can be seen in the two examples below). The numeral is always semantically plural.

Of is the most 'useless' element in the construction. It does not have a grammatical function, which will be the reason that it can be reduced or deleted. It is mostly deleted when there are two numerals in the construction:

In case the numeral in this construction is twatwo, of is often deleted, for example:

Next to this example, there is one case where of is deleted obligatorily:

This lexicalised expression is not very recognizable as an in N of Num construction, but it has some properties which are characteristic. The main one is the element in at the beginning. Furthermore, the noun has the same properties and restrictions as other nouns in this construction. Thus we also find expressions as in in oeremannicha couple of hours or in kearmannicha few times.

Instead of a numeral, the quantifier wat can also appear in the construction in N of Num:

Here, deletion of of is out, in contrast to the construction with the quantifier mannich in (21). Also modification of wat is not possible:

The expression in stik of wat functions as a quantifier in itself, meaning some or a couple of. Therefore the expression may be followed by a noun that is quantified, for instance in in stik of wat jierappelsa couple of potatoes. Next to the construction in stik of wat, the position of wat can be occupied by a numeral:

Cardinal numbers can also be used as names for ranks, scores, bank notes etc. (ik hie in tsienI had a tenI had the highest score) and then they behave like nouns, with the possibility of diminutive formation, pluralization etc. In diminutive formation, the cardinal gets an diminutive suffix, as in: tsientsjeten guilder/euro bill (or the Dutch loanword tientje), healtsjehalf a serving, certain coin and twaketwo eggs in a nest.

Multiplicatives are expressed by the cardinal numbers plus keartime: trije kear fjouwer is tolvethree times four is twelve. The noun kear always remains singular: ien kearonce, trije kearthree times. Keartime may also occur with ordinals: de tweintichste kearthe twentieth time. The suffix -ris ([rəs]) likewise indicates how many times something has happened: twaristwo times or trijeristhree times (see (25)). Nowadays the suffix -ris is mainly restricted to written Frisian. The same goes for the suffix -resom[rəsom] (see (1) in -resom). This affix can be used to define the size of the group: trijeresomin/with a group of three.

The cardinals hûndertone-hundred, tûzenthousand, miljoenmillion and miljardbillion can be considered a subset of the category of measure nouns (Booij (2010)). They have properties of nouns, in that they can be pluralized: hûndertenhundreds and tûzenenthousands. Hûndertone-hundred and tûzenthousand are different from miljoenmillion and miljardbillion, in that they can be used without a preceding numeral (a), where miljoen and miljard cannot (b) and (c):

Note that also the indefinite pronoun may count here as "preceding numeral":