Is DDR4 RAM compatible in a DDR3 RAM slot?

Is DDR4 RAM compatible in a DDR3 RAM slot? does ddr3 fit in ddr4 slot No, you can't use DDR3 on a board that has DDR4 memory slots only They won't fit and won't work does s21 ultra have s pen slot No, you can't use DDR3 on a board that has DDR4 memory slots only They won't fit and won't work

does nintendo switch lite have game card slot DDR4 **STORAGE:** 256SSD **AUDIO:** Audio by Bang & Olufsen DDR3 1600 MHZ ✓ Storage : 128GB SSD storage M2 ✓ Bluetooth