You have a lumpsum amount — invest it all today, or spread it out in equal instalments over a period? Compare the outcome under your assumed return rate.
Investing the full amount as a lumpsum today means all your money starts compounding immediately for the entire horizon. Spreading it out as a SIP means each instalment only starts compounding from when it's invested — so the last instalment gets much less time to grow. Mathematically, for a constant assumed rate of return, investing the full lumpsum immediately almost always produces a higher final value simply because more money is invested for longer. The real-world case for spreading it out is about managing the risk of investing everything right before a market downturn (called timing risk), not about the pure math of compounding.
If markets are already at reasonable valuations and you have a long time horizon, investing the lumpsum immediately typically gives more time in the market, which often wins mathematically. If you're worried about investing right before a market drop, spreading it out (called STP - Systematic Transfer Plan) reduces that specific risk, at the cost of some money sitting uninvested longer.
An STP (Systematic Transfer Plan) moves a lumpsum you already have from a low-risk fund (like a liquid fund) into an equity fund gradually, over a chosen period — effectively simulating a SIP using money you already possess, rather than fresh monthly income.