nucleosynthetic

The story

1. Proto-Italic*knuks
2. Latinnux
3. Latinnucleu
4. Englishnucleus
5. Englishnucleo-
6. Proto-Indo-European*ḱe?
7. Proto-Indo-European*ḱómder.?
8. Proto-Indo-European*sem-der.?
9. Proto-Hellenic*ksún
10. Ancient Greekσύν (sún)
11. Ancient Greekσυν- (sun-)
12. Proto-Indo-European*dʰeh₁-
13. Proto-Indo-European*dʰédʰeh₁ti
14. Ancient Greekτίθημι (títhēmi)
15. Ancient Greekσῠντῐ́θημῐ (sŭntĭ́thēmĭ)
16. Ancient Greekσύνθεσις (súnthesis)
17. Ancient Greekσυνθετικός (sunthetikós)
18. Frenchsynthétique
19. Englishsynthetic
20. English todaynucleosynthetic

From nucleo- + synthetic.