If you want to understand how old a man can be considered a young man, you must imagine that the use of such an expression has two sides: colloquial and legal.
Conversational meaning and physiology
Young man is an extremely common address and expression. In Russia, until 1917, this appeal was applied to a man under 50. He began to be considered the best groom, acquired sufficient life experience, a position in society, accumulated material wealth, only having reached this age. Most often, when meeting a man of fifty, the girls decided to marry him. Younger candidates were rarely considered.
From the point of view of biology, there are several age periods for men. This list contains: junior schoolchildren from 6 to 12 years old, adolescents from 10 to 18 years old, boys from 17 to 21 years old. Mature men are divided into 2 periods: the first from 21 to 35 years old and the second from 35 to 60 years old. As you may have noticed, science does not single out a specific "young" period.
Green, early, young, minor, young, young - all these are synonyms of the word "young" according to N. Abramov's dictionary of synonyms.
The colloquial meaning of the word "young" means being at the age of adolescence ("minor" - ancient Serbian, "boy" - Bulgarian) to mature years. Not old yet. Figuratively, one who has recently appeared has arisen. They also say "young man", meaning a man who has retained the vigor characteristic of youth in adulthood.
Based on these definitions, we can conclude that with the phrase "young man" you can refer to a man, starting from birth (green, early), ending 35 years.
If you are concerned about the issue of late paternity, for example, medicine here mentions age - 40 years, some sources - 50 years. That is, everyone who is younger is young men.
Legal aspect
From a legal point of view, young people in Russia were considered citizens between the ages of 14 and 30, as stated in the Strategy of State Youth Policy in the Russian Federation, approved on December 18, 2006. But today we can observe a shift in the age threshold for the category "youth" under 35 years old.
From a scientific point of view, it is impossible to determine the age of a person without documents. The development and maturation of a person, men, in particular, is a purely individual process. Therefore, when referring to an unfamiliar man on the street, in transport, or in any other public place, the neutral, respectful phrase “young man” is often used.
