what is the difference b/w disinvestment & privatisation? Greater degree of disinvestment always leads to privatisation?

Disinvestment is when government sells a portion of its shares to raise money. The government can continue keeping majority stake though and thus control the decision making process.
Privatisation refers to transfer of ownership from public to a strategic buyer in the private sector. Complete control is thus transferred to the private buyer.

disinvestment is just selling away of certain number of shares to a private entity thereby decreasing the governments own share. gradual disinvestment will ultimately lead to privatization as more and more shares are sold away by the govt to the private entity.

To explain in easy terms
Consider you have a publc company.... The total share is 100 initially...
Disinvestment is you sell some shares suppose 20 shares to public or private owners... You have 80 in hand... but 20 private people added.
Privatisation is you have only 49 shares private people has 51 shares means you are not owner for the company....
Hope it helps