“Sanyasi is the one who renounced the world. He has no attachments and no emotions what so ever. It is immaterial for him whether his own family member (say wife or mother or son or so) is in misery or joy or so. He lives in his own world which is God. He does not bother about his food even. He is not worried how his food comes for tomorrow or the next day or so. He is also not worried about his clothes or shelter or so.
Yogi is a self controlled person. Yogi is the one who has got total control on himself. If he wants to sleep, he can immediately sleep. If he wants to sit at one place for 10 hours, he will be able to sit. If he closes his eyes and does not want to listen to anything, even sounds of bomb blasts also do not reach him. Normal human being wants to control eating high calorie food (say). But, he is unable to control. Though he wants to avoid high calorie food, he can not. Means, he cannot do what he wants. Means, he is not Yogi. Yogi is the one whose mind and senses are totally under his control. He can order his mind to think or not to think of a thing. Thats all. Mind shall be totally in his control. In a way, it can be told that Yogi is the one who has highest will power.
Some yogis command their mind to remain happy always and to remain always in such happiness and joy. So, the mind obeys. Means, they are always happy in the recollection of God’s glories, God’s supremacy etc. In a way, they can be called as spiritual yogis.
Practically, Yogi is perceived as spiritual yogi without going into the technical definition of yogi.
Yogis may use their controlling power in positive and negative ways.
A sanyasi has to be a yogi. Otherwise, he cannot keep the emotions and attachments away.
A yogi need not be a Sanyasi.
Rishi is like a scientist. He explores the nature and gains the knowledge and passes onto the mankind. Knowledge about nature is knowledge of God. He passes the knowledge by way of writing and composing hymns, songs etc in praise of God.
Rishi can be a sanyasi or not a sanyasi. Rishi has to be a yogi because, unless he is yogi, it is difficult for him to gain real knowledge of God.
Like this, you can find many words like muni, sidha etc. The difference between various words is very subtle and more of academic interest. Practically, most of the words are used interchangeably.”