You are a child until the age of 18 years.
A person is considered as a young person till 26 years (not by law).
According to the Civil Code (Nr. 40/1964 GBl.), minors are persons who have unless reached 18 years. From then on, a person becomes contractually capable (Exception: The legal capacity depends on the individual health situation. Thereupon, a 18 years old person will not become contractually capable.).
According to the Penal Code (Nr. 140/1961 Gbl.), children under 15 years of age are Doli incapax for their actions. Therefore young people are person over 15 years of age which haven´t reached their 18th birthday.
According to the Criminal Code from 2004 minors become relief which means a specific law exists, which regulate the requirements for criminal liability of minors and the penaltes therefore.