254 oja-o ‘teacher [male and sg.]’   oja-püi ‘teacher [female and sg.]’   *oja-na ‘teacher [male and sg.]’       255 ona-o ‘son’   ona-püi ‘daughter’   *ona-na ‘son’
The singular is marked by -püi for human feminine and exceptionally for nonhuman feminine. Phrased more appropriately, -püi marks human feminine gender and singular number and exceptionally, nonhuman feminine gender and singular number.
Like -na, the human masculine gender and singular number marker, -püi can close relative participles converting them into participal nouns.
256 a. modo kapi-püi ‘female teacher [sg.]’           b.  larü amodo-püi ‘female learner [sg.]’           c. ota katapüi ‘female cultivator [sg.]’           d. oho kasepüi ‘female paddy-pounder [sg.]’           e. korü-püi ‘female writer [sg.]’
The following constitutes evidence that -o, -na and -püi mark at the same time singularity and specificity :
257 [i]a oho se ‘to pound paddy’           b oho ka-se-püi ‘[one specific] female paddy-pounder’           *c oho ka-se-püi kali ‘one female paddy-pounder’           *d oho ka-se-püi kosü ‘three female paddy-pounders’
13	I’m not sure of this form, as ona could mean both ‘offspring’ and ‘male offspring’
[ii] a oho ka-se-na [one specific] male paddy-pounder’ *b. oho ka-se-na kali ‘one male paddy-pounder’ *c oho ka-se-na kosü ‘three male paddy-pounders’
In contrast, -pfo and -pfü mark gender to the exclusion of number and specificity, as pointed out earlier.
258 a. mod pi ‘to teach’           b. modo ka-pi-müi-pfo ‘[any] male teacher[s]’           c. modo kapi-müi-pfü ‘[any] female teacher[s]’
This difference as to the marking of specificity between -o, -na nd -püi on the one hand and -pfo and -pfü on the other, explains why -pfo and pfü can not nominalise relative participles while -o, -na and -püi can :
259 a. osa de ‘to weave’           b. osa ka-de-o ‘[one specific] male weaver’           c. osa ka-de-na ‘[one specific] male weaver’           d. osa ka-de-püi ‘[one specific] female weaver’           *e. osa ka-de-pfo ‘[any] male weaver’           *f osa ka-de-pfü ‘[any] female weaver’
pfo and pfü, however, can precede [redundantly] the specific NG markers in participal nouns or follow -müi which agentivizes absolute nominals and nominalizes relative participles, as pointed out earlier.
260 a. modo ka-pi-pfo-na ‘male teacher’           b. modo ka-pi-pfü-püi ‘female teacher [participal nouns]’         261  a. duka-müi-pfo ‘[any] male shop-keeper’           b. duka-müi-pfu  ‘[any] female shop-keeper’       [absolute nominals]