Sanskrit
रजस्तमश्चाभिभूय सत्त्वं भवति भारत । रजः सत्त्वं तमश्चैव तमः सत्त्वं रजस्तथा ॥
rajas tamaś cābhibhūya sattvaṃ bhavati bhārata rajaḥ sattvaṃ tamaś caiva tamaḥ sattvaṃ rajas tathā
Translation
Now Harmony prevaileth, having overpowered Motion and Inertia, O Bhârata; now Motion, having overpowered Harmony and Inertia; and now Inertia, having overpowered Harmony and Motion.
Annie Besant · The Bhagavad-Gita, translated by Annie Besant (4th ed., 1922) — Wikisource · Public Domain
Explanation
An important structural point easy to miss: the gunas aren’t fixed proportions describing a person once and for all, they’re in constant competition, each temporarily overpowering the other two. Nobody is purely sattvic, rajasic, or tamasic — character and mood are a shifting equilibrium. That’s precisely why verses 11-13 are needed next: if dominance changes, a person needs observable signs to tell which guna is currently ascendant in themselves.