Developmental Pattern of Postpositional Markers (Josa) Use in Korean Children Aged 2–5 Years: A Focus on Frequency and Speaker Ratio

Objectives: Josa (Korean postpositional markers) play a crucial role in syntactic development by marking grammatical relations and clarifying semantic roles in Korean. This study examined the developmental patterns of josa use in children aged 2 to 5 years.Methods: A total of 240 typically developing children aged 2;0–5;11 participated, with 60 children per age group. Spontaneous language samples were collected during conversational interactions, and 50 utterances per child were analyzed. Measures included the frequency and number of josa types and the number of children producing each josa type. One-way ANOVAs examined age-group differences in overall and category-specific token and type counts. Josa types were ranked by frequency and speaker ratio within each age group.Results: Both the frequency and number of josa types increased significantly with age. Frequency-based analyses showed an increase in high-frequency josa types across age groups. The most frequently used josa across all ages were auxiliary particles (eun/neun), do, and yo, the nominative particle i/ga, and the predicative particle (i)ya/da. Low-frequency josa also showed a slight age-related increase, mainly among auxiliary particles. Speaker-ratio analyses indicated that the number of josa types produced by at least 75% of the children increased with age, with most josa types shifting toward higher speaker-ratio ranges in older groups. Rank orders based on speaker ratio were similar to those based on frequency.Conclusion: Josa use expands quantitatively with age, accompanied by systematic changes in usage patterns and distribution across age groups. These findings provide objective developmental data for language assessment and intervention planning.