Question

What is nucleosynthesis? How is it related to the Big Bang?

Answer 1

Nucleo-synthesis is the process of creating atomic nuclei heavier than hydrogen.
Nucleo = Nuclei
Synthesis = joining, merging.

Explanation:

In the early days of the Universe there were only protons, neutrons and electrons. Nucleo-synthesis is required to make the heavier elements.

Soon after the Big Bang, the so called "Big Bang Nucleo-synthesis" took place which created helium and traces of lithium and beryllium.

In modern times nucleo-synthesis takes place in stars, supernovae and cosmic ray interactions.