SCRIPT: A Subcharacter Compositional Representation Injection Module for Korean Pre-Trained Language Models

Korean is a morphologically rich language with a featural writing system in which each character is systematically composed of subcharacter units known as Jamo. These subcharacters not only determine the visual structure of Korean but also encode frequent and linguistically meaningful morphophonological processes. However, most current Korean language models (LMs) are based on subword tokenization schemes, which are not explicitly designed to capture the internal compositional structure of characters. To address this limitation, we propose SCRIPT, a model-agnostic module that injects subcharacter compositional knowledge into Korean PLMs. SCRIPT allows to enhance subword embeddings with structural granularity, without requiring architectural changes or additional pre-training. As a result, SCRIPT enhances all baselines across various Korean natural language understanding (NLU) and generation (NLG) tasks. Moreover, beyond performance gains, detailed linguistic analyses show that SCRIPT reshapes the embedding space in a way that better captures grammatical regularities and semantically cohesive variations. Our code is available at https://github.com/SungHo3268/SCRIPT . Top-10 MOD Samples Usage past tense, past connective form, ... past adnominal form, participial modifier, … connective ending, conditional clause, … adnominal form, nominal clause, conditional form, … compound modifier, experiential participle, … future adnominal form, speculative expression, … compound verb connective form, … passive past adnominal form, result expression, … passive past tense, perfective aspect, … declarative connective form, cause conjunction, … MOD Subcharacter-level MOD Character-level MOD Distribution of MOD -tagged characters 7.25% 92.75% Character Tag MOD-(하, 았) MOD-(하, ㄴ) MOD-(하, ㅏ) MOD-(이, ㄴ) MOD-(하, ㄴ) MOD-(하, ㄹ) MOD-(하, ㅏ) MOD-(되, ㄴ) MOD-(되, 었) MOD-(이, 라) MOD-Level Subchar (V+F) Subchar (F) Subchar (V) Subchar (F) Subchar (F) Subchar (V) Subchar (V) Subchar (F) Subchar (V+F) Character Original Char Modified Char