This study analyses variation sets in a sample of child-directed speech (CDS) in Turkish in terms of their structure and effect on child speech. The term "variation set" was first introduced to describe the sequences of repetitions, in which the intention behind expressions stays the same throughout the whole conversation while the form shows constant variation. This occurs in various ways such as lexical substitution, rephrasing and so on. This study attempts to investigate the speech of a child aged 1;8 in various conversations with a Turkish native speaker parent who engages in daily activities with her son. As a longitudinal study, the data was collected through video recordings for a period of three months covering the child's developmental stages from the age 1;8 to 1;10. The videos were recorded by the mother on a regular basis during day-time activities in play, meal and leisure times each week. Initially, the recorded data was transcribed and variation sets were identified. Later, they were analysed by looking at their structure and functions in the speech. Finally, the findings were compared with each other (in three sets) for the changes in frequency, structure and functions between the ages of 1;8 to 1;10. The data provide ample evidence on how variation sets in CDS are modified for a successful interaction without a communication breakdown in line with the child's linguistic competence.