sumbodhi wrote, “Citta is the “root” form of the word.”
Citta is not a word? Cittā (thoughts) is plural of citta (a thought.)
Here is a verse from dhammasaṅgaṇī: 2.4.2. Dukaatthuddhāra
“Katame dhammā cittā? Cakkhuviññāṇaṃ, sotaviññāṇaṃ, ghānaviññāṇaṃ, jivhāviññāṇaṃ, kāyaviññāṇaṃ, manodhātu, manoviññāṇadhātu—ime dhammā cittā.”