Abstract
The chapter deals with application of TTR index (type token ratio) to transcriptions of oral production of one Czech monolingual boy aged 2 years 8 months till 3 years 6 months. The boy was audiorecorded in spontaneous situations in interactions with adults.
The analysis proved that the child's vocabulary gets continuously larger, nevertheless, the text of the same lenght has to be analysed to avoid misinterpretation.