By 1939, it was spoken by as many as 15,000 people, and understood by as many as 100,000 (Zahn 1940). In the decade after World War II, the mission's network of schools managed to educate 30,000 students using Yabem as the medium of instruction (Streicher 1982). Although the usage of Yabem as a local lingua franca has now been replaced by Tok Pisin, Yabem remains one of the best documented Austronesian languages, with extensive instructional and liturgical materials (including many original compositions, not just translations from German or English) as well as grammars and dictionaries.
Glottal stop, written with a -c, is only distinctive at the end of syllables. The only other consonants that can occur syllable-finally are labials and nasals: p, b, m, ŋ. The liquid /l/ is realized as either a flap [ɾ] or a lateral [l]. Syllable-structure constraints are most easily explained if labialized and prenasalized consonants are considered unit phonemes rather than clusters. However, Otto Dempwolff, who greatly influenced the German missionary orthographies in New Guinea, apparently did not sanction labialized labials, preferring instead to signal rounding on labials by the presence of a round mid vowel (-o- or -ô-) between the labial consonant and the syllable nucleus, as in vs. ômôêŋ 'you'll come' vs. ômêŋ 'he'll come' or ômôa 'you'll dwell' vs. ômac 'you'll be sick' (Dempwolff 1939). (Compare the orthographies of Sio and Kâte.)
Yabem has a simple system of register tone that distinguishes high-tone syllables from low-tone ones. In the standard orthography, high-tone syllables are unmarked, while the nuclei of low-tone syllables are marked with a grave accent, as in oc 'sun' vs. òc 'my foot' or uc 'breadfruit' vs. ùc 'hunting net'. Tone distinctions in Yabem appear to be of relatively recent origin (Bradshaw 1979) and still correlate strongly with obstruent voicing contrasts (although not in its closest relative, Bukawa). Only high tones occur in syllables with voiceless obstruents (p, t, k) while only low tone occurs in syllables with voiced obstruents (b, d, g). The fricative /s/ is voiced in low-tone syllables but voiceless in high-tone syllables. Other phonemes are neutral with respect to tone, that is, they can occur in either high-tone or low-tone environments.
Verbs are prefixed to show the person and number of their subjects. (The 1st person plural exclusive and 2nd person plural prefixes are homophonous but can be disambiguated by using the free pronouns in subject position.) The singular prefixes also distinguish Realis and Irrealis mood (which usually translates to Nonfuture vs. Future tense). Each prefix also has a high-tone (H) and a low-tone (L) allomorph to meet the tone requirements of each of five conjugation classes. (See Bradshaw 2001.)
Preposed genitive pronouns are used to mark alienable possession by humans, as in ŋoc àndu 'my house', nêm i 'your fish', nê jàc 'his brother-in-law (wife's brother)'. Inalienable possession is marked by suffixes directly on the nouns denoting the possessions, which are typically kinship relations and body parts. The underdifferentiated suffixes are often disambiguated by adding the free pronoun in front of the suffixed noun. The final -i on the plurals of kin terms is a distributive marker, indicating some but not all of the class to which the noun refers. (See Bradshaw & Czobor 2005:21-29.)
Genitive relations for other than humans are not marked by either the genitive pronouns (for alienables) or the genitive suffixes (for inalienables). Instead, inherent possession of nouns as progeny or parts of wholes is marked by a prefix ŋa-, as in (ka) ŋalaka '(tree) branch', (lôm) ŋatau '(men's house) owner', and (talec) ŋalatu '(hen's) chick'. The same is true of adjectives (attributes of other entities) when derived from nouns, as in ŋadani 'thick, dense' (< dani 'thicket') or ŋalemoŋ 'muddy, soft' (< lemoŋ 'mud'). (See Bradshaw & Czobor 2005:26-31.)
Traditional counting practices started with the digits of one hand, then continued on the other hand, and then the feet to reach '20', which translates as 'one person'. Higher numbers are multiples of 'one person'. Nowadays, most counting above '5' is done in Tok Pisin. As in other Huon Gulf languages, an alternate form of the numeral '1' (teŋ) functions as an indefinite article. The numeral luagêc '2' can similarly function as an indefinite plural indicating 'a couple, a few, some'. The numeral root ta '1' suffixed with the adverbial marker -geŋ renders 'one, only one', while the numeral '2' similarly suffixed (luàgêc-geŋ) renders 'only a few'. Reduplicated numerals form distributives: tageŋ-tageŋ 'one by one', têlêàc-têlêàc 'in threes', etc. (See Bradshaw & Czobor 2005: 52-54.)
^Nordhoff, Sebastian; Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2013). "Yabem". Glottolog. Leipzig: Max Planck Institute for Evolutionary Anthropology.
Bisang, Walter (1986). "Die Verb-Serialisierung im Jabêm." Lingua 70:131–162.
Bradshaw, Joel (1979). "Obstruent harmony and tonogenesis in Jabêm." Lingua 49:189–205.
Bradshaw, Joel (1983). "Dempwolff’s description of verb serialization in Yabem." In Amram Halim, Lois Carrington, and S. A. Wurm, eds., Papers from the Third International Conference on Austronesian Linguistics, vol. 4, Thematic variation, 177–198. Series C-77. Canberra: Pacific Linguistics.
Bradshaw, Joel (1993). "Subject relationships within serial verb constructions in Numbami and Jabêm." Oceanic Linguistics 32:133–161.
Bradshaw, Joel (1998). "Squib: Another look at velar lenition and tonogenesis in Jabêm." Oceanic Linguistics 37:178-181.
Bradshaw, Joel (1999). "Null subjects, switch-reference, and serialization in Jabêm and Numbami." Oceanic Linguistics 38:270–296.
Bradshaw, Joel (2001). "The elusive shape of the realis/irrealis distinction in Jabêm." In Joel Bradshaw and Kenneth L. Rehg, eds., Issues in Austronesian morphology: A focusschrift for Byron W. Bender, 75–85. Pacific Linguistics 519. Canberra: Pacific Linguistics. ISBN 0-85883-485-5
Bradshaw, Joel, and Francisc Czobor (2005). Otto Dempwolff's grammar of the Jabêm language in New Guinea. Oceanic Linguistics Special Publication No. 32. Honolulu: University of Hawai‘i Press. ISBN 0-8248-2932-8
Dempwolff, Otto (1939). Grammatik der Jabêm-Sprache auf Neuguinea. Abhandlungen aus dem Gebiet der Auslandskunde, vol. 50. Hamburg: Friederichsen de Gruyter.
Ross, Malcolm (1993). "Tonogenesis in the North Huon Gulf chain." In Jerold A. Edmondson and Kenneth J. Gregerson, eds., Tonality in Austronesian languages, 133–153. Oceanic Linguistics Special Publication No. 24. Honolulu: University of Hawai‘i Press. amended version available online
Streicher, J. F. (1982). Jabêm–English dictionary. Series C-68. Canberra: Pacific Linguistics. (First compiled by Heinrich Zahn in 1917; later translated and revised by J. F. Streicher.)
Zahn, Heinrich (1940). Lehrbuch der Jabêmsprache (Deutsch-Neuguinea). Zeitschrift für Eingeborenen-Sprache, Beiheft 21. Berlin: Reimer.