Toba Batak language is one of the regional languages in Indonesia especially in North Sumatra province. Language cannot be separated from culture. What people mean is realized in language. Therefore, linguistics and cultures are the centre of analysis in the process of translating human's activities (Sembiring, 2016: 1142). In most villages in Tano Batak `Batak Land' such as Samosir sub district, Toba Samosir sub district, Humbang Hasundutan sub district, and Tapanuli Utara sub district Toba Batak language is used in daily social interaction. A person might utter one sentence in different ways depends on where he is, with whom he is speaking to, etc. (Ambarita, 2017a: 8557). Toba Batak language belongs to Austronesian spoken by 3 million people in Sumatra (Crystal, 1993: 40). There have been a lot of studies on generative morphology, such as Loe (2018); Zainuddin (2012); Nasution (2011); Sukri (2008); Simpen (2008); Murdiyanto (2000); etc.
2. Literature Review
A brief note on word formations
Morphology is the study of morphemes and their arrangements in forming words (Haspelmath et al, 2002: 1). Morphemes as elements of words play important roles in word formation, therefore, there are a lot of morphological issues that can be discussed, not only free morphemes but also bound morphemes (Ambarita, 2017d: 131). In other words, a base morpheme can be modified in order to form new word by affixation processes (Ambarita, 2017c: 131). Affixations are divided into four types, namely, prefixations, infixations, suffixations, and multi affixations.
According to generative morphology in Halle's model (1973), the rules of word formation would then tell us among other things how the morphemes are to be arranged in sequences to form actual words (Halle, 1973: 4). Halle suggested that morphology consists of three distinct components, they are: (1) List of Morpheme, (2) Word Formation Rules, and (3) Filter containing the idiosyncratic properties of words. One can think of the morphology, then, as producing a long list of words is designated by the term dictionary [8,5,7].
List of Morphemes includes roots, stems, bases, and affixes. It is the Word Formation Rules that determine how the morphemes of a language are arranged in sequences to form the actual words of that language. Word Formation Rules must be able to generate all the well-formed words of a language and exclude the ill-formed ones. The words of a language, however, cannot be derived wholly by means of regular rules because there exist semantic, phonological, and lexical idiosyncrasies (Scalise, 1984: 25). Halle proposes to treat such words in Filter. The words that actually pass through the Filter constitute Dictionary of the language as the final component.
3. Research Method
This study applied qualitative descriptive method. This study is intended to describe the real phenomena of Toba Batak language. This study is both documentary and field research because the data were originated from written and oral sources.
In reference to word formations in generative morphology (Halle, 1973: 8) there are four integrated components required, they are List of Morphemes, Word Formation Rules, Filter, and Dictionary.
List of Morphemes
Parts of word formations in List of Morphemes are realized as roots, stems, bases, and affixes. List of Morphemes in Toba Batak language are manifested in free word root, stems, bases, and affixes, such as prefixes, infixes, suffixes, and multi affixations (Ambarita, 2017b: 191). The affixes that can generate nouns in Toba Batak language is discussed in the following parts. Apart from free word bases, affixations are the other elements of List of morphemes. This study found that nominal affixations in Toba Batak language are distinguished into five types of affixations, they are:  prefixes (e.g. par-, na-, sa-, sanha-, hina-, and ha-),  infixes (e.g. –ar- and –al-),  suffix (e.g. –an),  multi affixations (e.g. ha-...-on, pa-...-an, pa-...on, and par-...-an), and  double affixations (e.g. par-in-).
Word formation rules
Nominal word formations as the central issue in this study can be derived from various free word bases, such as, free adjectival bases, free verbal bases, free nominal bases, free numeric bases, and free adverbial bases. The results of these affixations can be inflectional or derivational.
Nominal word formations
Based on the data collected, nominal word formations in Toba Batak language are distinguished in 3 main ways, they are:  by attaching affixations,  by inserting premodifier ni between adjectival bases and nominal bases, and  by moving the stress of free adjectival bases from the first syllable to the second syllable.
Prefix par- can be inflectional and derivational. Prefix par- is inflectional if it is attached to free nominal bases as in the following data.
 parhuta `villagers'
 parhoda `the horse's owner'
The forms parhuta and parhoda as complex words are formed from free nominal bases huta `village' and hoda `horse' respectively by attaching prefix –par. The attachment of prefix par- both to huta and to hoda as nouns does not alter the word class. Therefore, prefix par- is inflectional. Besides, prefix par- can also be derivational if it is attached to free verbal bases as in the following data.
 parkarejo `worker'
 parjuji `gambler'
The attachment of prefix par- both to karejo `work' and to juji as verbs changes the word class to noun. Therefore, prefix par- is inflectional. The meaning of prefix par- in this context is person who .... as indicated by the free verbal bases karejo and juji. Juji is a precategorial lexeme or a stem which does not have syntactic category. It can only have meaning after affix is attached. There is another variation of prefix par- to negate expression as shown in .
 par-dang-girgir `unhappiness'
Par-dang-girgir is formed from free adjectival base girgir `happy' + dang `not' - dang girgir `will not'. Furthermore, prefix par- is attached to dang girgir - par-dang-girgir `unwillingness'. Prefix par- in this word formation is derivational because it changes the word class from adjective becomes noun.
Prefix na- functions as derivational affix if it is attached to free adjectival bases as in the following data.
 natigor `fair person'
 namalo `clever person'
From data  and  it can be seen that prefix na- is derivational because its attachment to free adjectival bases tigor `fair' and malo `clever' respectively changes the word class to nouns. The combination of prefix na- to free adjectival base encodes person as indicated by the base morpheme to which the affix is attached.
Prefix sa- is inflectional if it is attached to free nominal bases as in the following data.
 sandangka `one branch (of fruit)'
 sansisir `one bunch (of banana)
The free nominal bases of sandangka and sansisir are dangka `branch' and sisir `scraper'. Prefix sa- is a bound morpheme. Thus, sa- + dangka - *sadangka and sa- + sisir - *sasisir. There is phonological idiosyncrasy in  and . Therefore, these forms must enter FILTER to have morphophonological processes.
Deep Structure: *[#[sa-]pref + [daηka] NP#]N
Additional phoneme /n/: *[#[sa-]pref + /n/ + [daηka] NP#]N
Surface Structure: sandangka
Deep Structure: *[#[sa-]pref + [sisir] NB#]N
Additional phoneme /n/: *[#[sa-]pref + /n/ + [sisir] NB#]N
Surface Structure: sansisir
The forms sandangka and sansisir are now ready to be put into dictionary.
Prefix sanha- belongs to inflectional affix because its attachment to free word base does not change the word class as presented below.
 sanhabona `one trunk (of tree)'
 sanhababa `one piece (of word)'
The forms sanhabona and sanhababa are complex words formed from free nominal bases bona `trunk' and baba `mouth' as simple words. The combination of the two morphemes brings new meaning to prefix sanha- that is one.
Prefix ha- can be attached to free verbal bases, free numerical base, and to free adjectival bases. However, there is a special word formation rule for this category. The first syllable of verb or adjective to which prefix ha- is attached is doubled until vowel sounds as follows.
 haboborhat `departure'
 haoopat `the four'
 hariringgas `diligence'
The forms haboborhat, haoopat, and hariringgas are formed from simple words borhat, opat, and ringgas by attaching prefix ha- added by the first syllable of the word until vowel sound. The first syllables of the word borhat, opat, and ringgas are bor-, o-, and ring- respectively. The forms bor-, o-, and ring- as the first syllables of those words until vowel sound are bo- from bor-, o-, and ri- from ring-. Later, bo-, o-, and ri- are attached to borhat and ringgas which generate bo-borhat, o-opat, and ri-ringgas. Finally they are added by prefix ha- to form ha-bo-borhat, ha-o-opat, and ha-ri-ringgas. Based on the data above, prefix ha- is derivational.
Prefix hina- can be attached to free adjectival bases as in the data below.
 hinadenggan `kindness'
 hinaroa `ugliness'
The function of prefix hina- is derivational if it is attached to free adjectival bases. The forms hinadenggan and hinaroa are formed from simple words denggan and roa respectively. The meaning of prefix hina- in this data is the quality of being .... as mentioned by the free adjectival bases. There is another variation of prefix hina- to negate expression as shown in .
 hina-so-olo `unwillingness'
Hina-so-olo is formed from free adjectival base olo `will' + so `not' - so olo `will not'. Furthermore, prefix hina- is attached to so-olo - hina-so-olo `unwillingness'. Prefix hina- in this word formation is derivational because it changes the word class from adjective to noun.
Prefix ha- as a derivational affix can integrate with word combination in which the base of the word combination is adjectival bases.
 ha-so-ra-malumon `the impossibility to get recovered'.
 ha-hurang-turean `the quality of being less kind'
 ha-dang-olo `unwillingness'
 ha-nabadiaon `the quality of being holy'
The form ha-so-ra-malumon is a very complex word combination which is formed from free adjectival base malum `recovered'. The sequence of processes to form the word ha-so-ra-malumon is started by presenting premodifier ra `possible' to malum - ra-malum. Later, premodifier so `not' is attached to ra-malum - so-ra-malum `not possible to get recovered'. Finally, confix ha-...-on is attached to so-ra-malum - ha-so-ra-malumon `the impossibility to get recovered'. The same procedures also occur to , , and .
Infix -par- can be inflectional and derivational. Infix -par- is inflectional if it is attached to free nominal bases, such as in , , , and .
 darede `saliva'
 barungbung `a valley between two mountains'
 haratak `sound tak-tak-tak
 haruok `the name of bird of which the sound is huok huok huok'
The forms darede, barungbung, haratak, and haruok as complex words are formed from nominal bases morphemes dede `a drop of saliva', bungbung `a big open hole', hatak `sound tak', and huok `sound huok'. The attachment of infix –ar- to nominal bases indicates plural or look like .... as indicated by the nominal bases. Infix –ar- can also be attached to verbal base category as in  and .
 hariar `the handle of a spoon'
 garantung `traditional musical instrument for Toba Batak ethnic consisting of five pieces hung when they are played'
The forms hariar and garantung are complex words. They are formed from simple forms hiar `scrape (sth, usually rice) out of container' and gantung `hang' as transitive verbs that need the presence of objects in sentence valence. The attachment of infix -ar- both to hiar and to gantung as verbs alters the word class becomes nouns. Therefore, infix –in- is derivational. The meaning of infix –ar- shows the noun of the verbal bases. Infix –in- can also be attached to free adjectival base, such as in  below.
 harungkut `contraction'
The form harungkut is a complex word which is formed from lexeme hungkut `wrinkled' by attaching infix –in- within the free adjectival base hungkut. Therefore, infix –in- + hungkut - harungkut.
Infix –al- is an alternative usage of infix –ar- that can be inserted within free nominal base. In this context, dental phoneme /r/ and /l/ are interchangeable reciprocally as shown in the following data.
 hosuk `civet' - halosuk /harosuk `civets or civets like'
 gunsang `shake' - galunsang/garunsang `sea wave'
 gege `torture' - galege /garege `troublemaker'
 tindan `crooked' - talindan /tarindan `crooked root'
Suffix –na is a derivational affix because it changes the word class to which the affix is attached as in the following data.
 ulina `beauty'
 timbona `height'
Ulina and timbona are formed from uli and timbo as adjectives. It can be seen clearly that the attachment of bound morpheme –na to free adjectival base changes the adjectives becomes nouns. Therefore, suffix -na is a derivational affix.
Multiple affixations ha – on
Multiple affixations ha-...-on is a derivational affix as presented in the following data.
|No||Adjectival Base||Gloss||ha-...-on||Gloss||Form Change|
|35||hipas||healthy||hahipason||health||Adj - N|
|36||mora||wealth||hamoraon||wealthy||Adj - N|
The forms hahipason, hamoraon, hasangapon, and hajorbuton as complex words are formed from adjectival base morphemes hipas, mora, sangap, and jorbut respectively by attaching multiple affixations ha-...-on.
Multiple affixations pa- ... -an
Multiple affixations pa-...-an is a derivational affix because it changes the free verbal base to noun as in the following data.
 lompa - pangalompaan
 sungkun - panungkunan
 seat - paneatan
 pele - pamelean
Those forms must enter filter to be processed.
Deep Structure: *[#[pa-an]M. Affixations + [lompa] VB#]N
Additional phoneme /ηa/: *[#[pa-an]M. Affixations + /ηa/ + [lompa] VB#]N
Surface Structure: pangalompaan
Similar process also occurs to other data.
Multiple affixations pa- ... -on
Multiple affixations pa-...-on is a derivational affixation because it changes the free verbal base to noun as in the following data.
antusi + pa-...-on - pangantusion
tanom + pa-...-on - pananomon
pinsang + pa-...on - pamissangon
hophop + pa-...-on - panghophopon
The forms pangantusion, pananomon, paminsangon, and panghophopon as complex words are formed from free verbal bases antusi, tanom, pinsang, and hophop respectively by attaching confix pa-...-on. Free verbal bases antusi + pa-...-on - *paantusion, tanom + pa-...-on - *patanomon, pinsang + pa-...-on - *papinsangon, hophop + pa-...-on - *pahophopon. These forms cannot enter DICTIONARY before they are processed in FILTER.
Deep Structure: *[#[pa-on]M. Affixations + [antusi] VB#]N
Additional phoneme /η/: *[#[pa-on]M. Affixations + /η/ + [antusi] VB#]N
Surface Structure: pangantusion
Deep Structure: *[#[pa-on]M. Affixations + [tanom] VB#]N
Phoneme assimilation /n/: *[#[pa-on]M. Affixations + /n/ + [tanom] VB#]N
Surface Structure: pananomon
Deep Structure: *[#[pa-on]M. Affixations + [pinsaη] VB#]N
Phoneme assimilation /m/: *[#[pa-on]M. Affixations + /m/ + [pinsaη] VB#]N
Surface Structure: paminsangon
Deep Structure: *[#[pa-on]M. Affixations + [hokkop] VB#]N
Additional phoneme /η/: *[#[pa-on]M. Affixations + /η/ + [antusi] VB#]N
Surface Structure: panghophopon
The form pangantusion, pananomon, paminsangon, and panghophopon are now ready to be put into dictionary.
Multiple affixations par- ... -an
Multiple affixations par-...-an can be attached to verbs as in the following data.
The forms pardahanan, parsaoran, parmanganan, and parjujian as complex words are formed from free verbal bases dahan, saor, mangan, and juji respectively by attaching confix par-...-an. The attachment of multiple affixations par-...-an to free verbal bases changes the word class from verb to noun.
Multiple affixations par-...-an can also be attached to nouns as in the following data.
The forms parsingkolaan, parjabuan, parbornginan, and pargadongan as complex words are formed from free nominal bases singkola, jabu, borngin, and gadong respectively by attaching confix par-...-an. Multiple affixations par-...an is an inflectional affix.
Double affixations par-in-
Double affixations are derivational affixes as in  and .
 parsinuan `father'
 parsinonduk `wife'
Double affixations in parsinuan and parsinonduk are the combination of prefix par- and infix –in-. Thus, the base forms of the two complex words are suan `plant' and sonduk `scrape (sth, usually rice) out of container' respectively. The meaning of the double affixations is to form figurative expressions.
Inserting premodifier ni between adjectival bases and nominal bases
Besides attaching affixations, inserting premodifier ni between adjectival bases and nominal bases also can form nouns as in  and .
 Dang tarpatudos uli ni Tao Toba hu tao na asing
not compared beautiful [PREMODIFIER] Lake Toba to lake which others
`The beauty of Lake Toba cannot be compared to other lakes'
 Ise umboto timbo ni Gunung Toba najolo?
Who know high [PREMODIFIER] Mount Toba formerly?
`Who knows the height of Gunung Toba formerly?'
Based on these two sentences, it can be seen clearly that lexemes uli `beautiful' in  and timber `high' in  are adjectives. However, the presence of premodifier ni in the sentences changes the lexical category of uli `beautiful' (adjective) - uli ni `beauty' (noun) and timbo `high' (adjective) - timbo ni `height' (noun). In short, by the presence of premodifier ni between free adjectival bases and noun has transformed free adjectival bases to nouns.
Moving the stress of free adjectival bases from the first syllable to the second syllable
The last way of forming nouns in Toba Batak language is by moving the stress of free adjectival bases from the first syllable to the second syllable as in , , and .
The forms `garemor, `harumor, and `garelllok are adjectives with infix –ar- of which the stress of the words is in the first syllable. However, those words can be generated into nouns by changing the stress of the words to the last second syllables.
As a theory of which has predictive power, generative morphology is eligible to be applied in language studies to explore language phenomena without exception. The theory stimulates the way of thinking critically. In so doing, other researcher especially linguistic students of master degree and doctoral degree are hoped to do other research using generative morphology to develop new theory. In other words, further research is expected to be theory finding rather than theory application.