Is masturbation considered sex?

People tend to connect the word sex the meaning that feels right to them. That is the meaning that os in tune with their culture, personal values and experience. 

For many people, having sex refers only to activities that involves penetration- that is penis into the vagina or penis into anus. For others sex also include oral sex. For yet others, sex covers all activities involving the stimulation of sexual organs, including masturbation. 

Whatever interpretation is most aligned with your feelings and values, there is one thing everybody should agree with; any direct stimulation of the sexual organs that is intended to cause arousal and that could lead to orgasm is a sexual activity. 

Although masturbation is generally less intense than many activities involving stimulation of the genitals, it is still very much a sexual act.