What are the signs of someone being Baligh?

There are three signs of reaching Bulugh (Maturity):

1. The discharge of semen[1].
2. The growth of coarse hair in the pubic[2] region.
3. The completion of fifteen (15) years for boys, according to the lunar calendar, and the completion of nine (9) years for girls, according to the lunar calendar.

It is not necessary to see all three of the above mentioned signs to be sure of one being Baligh. Rather, seeing even one of these signs confirm this. Therefore, if semen is discharged from a youth, even if he is not yet reached to the age (as mentioned previously), he will be (considered as) Baligh, and must act according to the laws of Islam.