Today is this day, the one you are standing in. The date at the top of the newspaper, the list of things to get done before it goes dark, the answer to 'when?' that means now and not tomorrow.
It works as an adverb — I will call you today — and as a noun: today is Thursday, today's news, the paper for today. It stretches to mean the present age as well: young people today, the world today, today's students. No preposition goes in front of it, so say I am leaving today and never on today. The neat set is today, tonight, tomorrow, and yesterday sits outside it with no matching to-. Here today, gone tomorrow is the phrase for anything that will not last.
1adverbtodayOn this day; on the day that is happening now.~2%
“The results come out today at noon.”
2noundayThis day.~2%
“Today is the last chance to send the form back.”
3nounpresentThe present time, the age we are living in.~96%
“Children today learn to type before they learn to write.”
Shares are an estimate: a language model read 10 sentences found in the wild and placed 10 of them on a sense — a count of our sample, not a measurement of English.
Today began as two words in Old English: tō dæġe, 'on the day', which is nothing more than to plus day. It stayed loosely joined for centuries, and Middle English wrote it to-daie. Dutch does the same trick with vandaag, and Swedish with i dag.
Old English
tōdæġ
Middle English
today
English, today
today
Built from
From Middle English today, to-daie, todæig, from Old English tōdæġ, tō dæġe (“today”) literally “on [the/this] day, [this] day forward”, equivalent to to + day. Compare stq däälich (“today”), Dutch vandaag (“today”), Old Saxon hindag (“today”) literally “[this] day forward”, German Low German vandage, vandaag (“today”), Swedish i dag, idag (“today”).
Etymology from Wiktionary, CC BY-SA