I wanted to tell my boss that I will finish a project "tonight" but mid-sentence I realized I only work until afternoon, so I tripped over my words and said "I will finish it to...noon?" we both laughed and it got me thinking, why can we use words like today and tonight but not tomorning and tonoon?

  • 3
    Had English been designed by engineers and mathematicians I have no doubt you would be able to.
    – WS2
    Jun 25, 2015 at 21:09
  • Note, as GetzelR's answer tells you, that in effect we do say 'tomorning': morning and morrow are both descendants of the same OE form. Jun 25, 2015 at 21:19
  • To can only precede a day, not a precise time. Morning is related to morrow, which refers to a day, but morning itself, referring to the first part of the day, cannot be paired with to. They share a root, but I don't think morning is synonymous with morrow so tomorning is also out.
    – GetzelR
    Jun 25, 2015 at 21:42
  • @WS2 and we'd also have "fromorrow" instead of "yesterday"
    – JeffSahol
    Jun 25, 2015 at 21:47
  • 1
    You can certainly use "tomorning" and "tonoon" if you wish. There's no law against it.
    – Hot Licks
    Jun 25, 2015 at 22:55

1 Answer 1



The "to" in today means "on." Today means "on (this) day," tomorrow means "on (the) morrow."

"On" is used for days and dates, not times or parts of the day, so no tonoon or toevening.

I've been looking for an explanation of prepositions as they relate to time. The best I could find have been the rules without explanation.

[edit] At first glance, tonight seems to be an exception. However, many cultures, including the source of the word "night" at the time, reckoned by nights and night was sometimes used as a synonym for day to refer to a specific day. More broadly, in early times days were held to begin at night.

It is possibly in this sense/context, night being seen as a demarcation between days and referring therefore to the next day as it began, that tonight was coined in keeping with the rules of preposition.


Etymonline - Today

Today Old English todæge, to dæge "on (this) day," from to "at, on" (see to) + dæge, dative of dæg "day" (see day). [...] Generally written as two words until 16c., after which it usually was written to-day until early 20c.

Etymonline - Tomorrow

Tomorrow to morewe, from Old English to morgenne "on (the) morrow," from to "at, on" (see to) + morgenne, dative of morgen "morning" (see morn, also morrow). As a noun from late 14c. Written as two words until 16c., then as to-morrow until early 20c.

Etymonline - Night

Night Old English niht (West Saxon neaht, Anglian næht, neht) "night, darkness;" the vowel indicating that the modern word derives from oblique cases (genitive nihte, dative niht), from Proto-Germanic *nakht- (cognates: Old Saxon and Old High German naht, Old Frisian and Dutch nacht, German Nacht, Old Norse natt, Gothic nahts). [...]

The fact that the Aryans have a common name for night, but not for day (q.v.), is due to the fact that they reckoned by nights. [Weekley] Compare German Weihnachten "Christmas." In early times, the day was held to begin at sunset, so Old English monanniht "Monday night" was the night before Monday, or what we would call Sunday night. The Greeks, by contrast, counted their days by mornings.

One example of the sites listing preposition rules for time. None of the initial search results were for traditional authoritative sources, but it seemed sufficient.

  • 1
    But what about tonight then? Night sounds in the same category as noon and evening. My answer is, its just the way it is. Human spoken languages are not framed by a design committee.
    – nawfal
    Jun 26, 2015 at 2:11
  • Despite accepting, I agree that the answer doesn't cover the issue of "tonight" having the "on" relate to a time of the day.
    – bpromas
    Jun 26, 2015 at 11:54
  • 2
    I've added a section specifically addressing tonight
    – GetzelR
    Jun 26, 2015 at 13:41

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