Learn English – Is “to” a prefix in English


I was thinking about the words "today" and "tonight" and trying to think of what "to" means in these words. A cursory Google search turns up no results for "to-" in any prefix lists.

Best Answer

to (a prep.) : Old English to "in the direction of, for the purpose of.....

Commonly used as a prefix in Middle English (to-hear "listen to," etc.), but few of these survive (to-do, together, and time references such as today, tonight, tomorrow -- Chaucer also has to-yeere). (etymonline)