# Automatic Correction of Indonesian Grammatical Errors Based on Transformer
## 3 Grammatical Error Types in the Indonesian Language
* Affix usage: The incorrect affix usage will change the meaning of the main word, and this error is often made by language learners, such as with the words 'Nikmat = Menikmati = Kenikmatan', 'Cerai = Bercerai = Penceraian' and 'Jalan = Berjalan = Perjalan'. * Word order: This error is related to the structure or arrangement of words in sentences. Foreign learners often make this error because they make an analogy of word order in Indonesian with that in English, such as 'Hari menarik = _An interesting day_' with ('Menarik Hari') and 'Buku bagus = _A good book_' with 'Bagus Buku', among others. * Syntactic error: This error often occurs in incomplete sentences and ungrammatical sentences in Indonesian grammar procedures. Learners often omit the subject, predicate or object in a sentence so that the sentence is not fully understood. For example, they omit the object in the sentence ('Mereka menikmati banyak sekali = _They enjoy a lot_'), while the correct sentence is 'Mereka sangat menikmati malam-malam indah = _They enjoy the beautiful nights a lot_'. * Preposition usage: The use of inappropriate prepositions will change the meaning of the sentences. An example of incorrect preposition usage such as 'Mereka membeli sebuah buku **ke** Toko buku = _They buy a book **to** the bookstore_' should be 'Mereka membeli sebuah buku **di** Toko buku = _They buy a book **at** the bookstore_'. 2. Spelling Error: This frequently occurs while writing text, such as adding or deleting characters and missed spaces between words. These errors can be detected easily using a simple spell checker application. Examples include affix usage errors and incorrect conjunction usage. 3. Semantic error: These errors occur during writing as a result of incorrect use or misuse of pronunciation marks in the sentences, which leads to misunderstanding the reader. * Conjunction usage: Incorrect use of conjunctions is common among second language learners. Conjunctions are links between phrases, clauses and sentences. In order to avoid misinterpretation in sentences, we must use conjunctions correctly and appropriately, such as the use of the words 'Bahwa' and 'Walaupun', which are not correct in the context of the sentence. * Plural formation: The formation of plural words involves using plural markers such as 'Beberapa = _some_', 'Sedikit = _few_' and 'Banyak = _many_', numerals such as in '10 Buku = _10 books_' and the repetition of the noun itself, such as 'Toko-toko = _shops_'. However, language learners often use repeated plural words, such as in 'Banyak toto-toko tutup karena pandemi = _Many shop and shop are closed because of a pandemic_', and the correct usage is 'Banyak toko tutup karena pandemi = _Many shops are closed because of a pandemic_'. * Passive construction usage: Passive and active sentences are one of the toughest challenges for foreign learners. They often make errors between the two in sentences such as 'Stadion itu membangun untuk olahraga national = _The stadium build for national sports_', where the correct usage is 'Stadion itu dibangun untuk olaharaga national = _The stadium was built for national sports_'.