Step 1: Understanding Tripiṭakas.
The Tripiṭakas consist of three collections: Vinayapiṭaka (monastic rules), Suttapiṭaka (discourses of Buddha), and Abhidhammapiṭaka (philosophical analysis).
Step 2: About Saṃyuktanikāya.
The Saṃyuktanikāya is one of the five Nikāyas in the Suttapiṭaka, containing discourses grouped by themes.
Step 3: Analysis of options.
- Suttapiṭaka: Correct, it belongs here.
- Abhidhammapiṭaka: Contains philosophical texts, not Saṃyuktanikāya.
- Vinayapiṭaka: Deals with monastic rules.
- Vaṃsa literature: Refers to chronicles, not part of Nikāyas.
Step 4: Conclusion.
Thus, Saṃyuktanikāya belongs to the Suttapiṭaka.