Adverb
On that or this.
Source: Webster's dictionaryThere's a double beauty whenever a swan Swims on a lake with her double thereon. Thomas Hood
The platform of an Ethical Society is itself the altar; the address must be the fire that burns thereon. Felix Adler
It is greater than the stars - that moving procession of human energy; greater than the palpitating earth and the things growing thereon. Kate Chopin
Praise not, O man, the life beyond control, Nor that which bows unto a tyrant's sway. Know that the middle way Is dearest unto God, and they, thereon who wend, They shall achieve the end. Aeschylus
[He] spread his bread with all sorts of butter, yet none would stick thereon. Thomas Tusser
What the sick need is teachers not treaters, health schools not hospitals, instruction not treatment, education in right living not training the sick habit. Both they and their advisors must get rid of the curing idea and the practices built up thereon. Herbert M. Shelton