Q.When A Basil Plant Is Left Outside Through The Winter Will It Grow Back In The Spring?
If it doesn’t live through winter then does one need to plant a seed to get basil again?

Certified GKH Gardening Expert
Basil is an annual plant so if you have cold winters it will die out with the first freeze. In the spring, you can buy a seedling from a nursery or you can grow your own with seeds.
https://www.gardeningknowhow.com/edible/herbs/basil/how-to-grow-basil-plants.htm
https://www.gardeningknowhow.com/edible/herbs/basil/harvesting-basil-seeds.htm
https://www.gardeningknowhow.com/edible/herbs/basil/growing-basil-seeds.htm
https://www.gardeningknowhow.com/edible/herbs/basil/basil-watering-tips.htm
For care on the many varieties search here:
https://www.gardeningknowhow.com/edible/herbs/basil