ON Copy link • ONpreposition, (Of place or situation), to the question “where?” in, with ablative; e.g., to place on the table, ponere in mensa (☞ not mensam, because the idea of rest is already included in ponere, according to the Roman conception of the word): super with ablative (of a surface on which anything is): ad (near; e.g., ad Tiberim habere hortos, on the Tiber). In many cases where we think of a thing as at rest, the Romans fix on the previous direction and motion, and hence our “on” is to be rendered by ex, de, also, by a (ab); e.g., on a march or journey; ex itinere (also in itinere; yet with this difference, that in itinere = during the march, ex itinere = from the march, so that it was uninterrupted for some lime; Vid: Held, Caes., B.C., 1, 24): on the right, on the left, a dextra, ab laeva: on the side, a latere: to fight on the walls, de moenibus pugnare. “On” is expressed by the ablative alone, (a) with substantives of place; e.g., to post armed men on the walls, muris armatos disponere (Vid: Held, Caes., B.C., 1, 21): (b) in expressing a means and instrument which, in Latin, is already within the relation of the ablative case; as, to ride on a horse, equo vebi: to blow on a pipe, tibiis canere: (c) when the Latin preposition is already expressed in a compound verb; as, to sit on horseback, equo insidere. Observe, also, the following turns of expression: on the platform, pro rostris; pro suggestu (Vid: Zumpt, § 311): on the spot, e vestigio; statim; confestim (immediately): on the ground, humi (☞ in humum only in poetry): on all sides, quoquoversus: to hang on a tree, pendere ex arbore: on your authority, tua auctoritate te auctore: on this condition, hac lege or conditione: to be on anyone’s side, stare, facere, sentire, esse ab aliquo. (Of time), to the question “when?” by the simple ablative: on the fourth day, quarto die: on the day, die: on the morning, mane: sometimes employ cum; as, on the day that I thanked you, eo die, cum tibi gratias agerem. With a definite term or point of time at which anything is to take place, ad is used; e.g., to appear on a (fixed) day, ad diem convenire.