1 [count] : a period of 24 hours beginning at midnight : one of the seven time periods that make up a week ▪ We're open seven days a week, 365 days a year. ▪ Payment is due on the first day of every month. ▪ “What day is (it) today?” “Tuesday.” ▪ “What day [=date] is Friday?” “It's the 28th.” ▪ “What day of the week is the 28th?” “It's a Friday.” ▪ He spent five days in the hospital. ▪ She left on Thursday and came back four days later. ▪ The baby is due (to be born) in three days. ▪ That was the happiest day of my life. ▪ Parenthood gets better every day. ▪ We'll be finished in a day or two. = We'll be finished in a couple of days. ▪ It rained for a day and a half. [=it rained for about 36 hours] ▪ The office is closed for the day. ▪ I call him every (single) day. ▪ Tomorrow is another day. [=there will be more opportunities to do things tomorrow] ▪ a day of celebration/mourning [=a day for people to celebrate/mourn] ▪ Take one pill two times a day. [=each day] ▪ She works eight hours a day. ▪ It costs 10 dollars a day to park there. ▪ The party is the day after tomorrow. = The party is in two days. ▪ It happened the day before yesterday. = It happened two days ago. ▪ Sometimes they didn't speak to each other for days on end. [=several days] ▪ From that day forth/forward [=(less formally) from then on], I was determined to do better. ◊If you do not look a day over a particular age, you appear to be that age. ▪ “Today's my 50th birthday.” “Really? I'm surprised. You don't look a day over 40.” [=you don't look any older than 40 years old] ◊If you say that someone is a particular age if he/she is a day, you mean that the person is that age or older. ▪ The man she's dating is 60 if he's a day. [=he is at least sixty years old]
2 : the time of light between one night and the next : the part of the day when light from the sun can be seen [count] ▪ What a beautiful summer day! ▪ a cold/wet/rainy day ▪ The shortest day of the year is usually December 22, and June 22 is usually the longest. [noncount] ▪ He sleeps during the day [=daytime] and works at night. ▪ You can call me any time, day or night. ▪ These animals are mostly active during the day. ▪ I work during the day. [=I work days] ▪ She's a student by day [=during the day] and a waitress by night. ▪ I woke at (the) break of day. [=(more commonly) dawn, daybreak, sunrise] ▪ day workers [=people who work during the day] —opposite night
3 : the part of the day when people are usually most active and when most businesses are open [singular] ▪ I like to start my day with a cup of coffee. [=I like to drink a cup of coffee as soon as I wake up] ▪ We decided to rent a car for the day. ▪ How was your day? ▪ By the end of the day, we were all exhausted. ▪ Our neighbors play their loud music at all hours of the day. [=throughout the day] ▪ Let's go to bed. We have an early day [=we will get out of bed early] tomorrow. ▪ I needed to relax after a long day at work/school. [=after working/being at school for a long time] ▪ “Thank you, ma'am. Have a nice day!” [noncount] ▪ I'll be gone all day. ▪ It rained all day long. ◊People sometimes say that they can't wait all day or don't have all day when they are in a hurry and need someone to move or act more quickly. These phrases are usually used in a rude way. ▪ Hurry up! I can't wait all day! = I don't have all day. = I haven't got all day.
4 [count] : the hours during a day when a person works or goes to school or when a company does business ▪ I put in four twelve-hour days [=workdays] this week. ▪ She makes about 50 dollars a/per day. ▪ He was late for his first day on the job. ▪ They collected a full day's pay for half a day's work. ▪ We had a busy couple of days at the store. ▪ We have a short day tomorrow. [=we have to work fewer hours tomorrow than usual] ▪ The school committee is pushing for a longer school day. ▪ Tomorrow's our last day of school (for the school year). ▪ Please allow 14 business days [=days when most businesses are open; weekdays that are not holidays] for delivery. ◊If something is all in a day's work for someone, it is part of a person's typical work. ▪ Solving violent crimes is all in a day's work for these police detectives. ◊To take a/the day off is to decide not to work on a particular day. ▪ He took the day off to go fishing.
5 [count] : the day on which something specified happens or is expected to happen ▪ It rained on their wedding day. ▪ the day of his birth ▪ This Sunday is family day [=a day for families especially with young children] at the amusement park. ▪ If you've been waiting for the perfect skiing conditions, today's the day. [=the conditions are perfect today] ▪ So, when's the big day? When are you getting married? ▪ Did you ever think you'd see the day when he would apologize? [=did you believe he would ever apologize?] ▪ I never thought I would live to see the day when you would graduate from college. [=I did not think I would live long enough to see you graduate] ▪ Let her have her day in court [=let her defend herself in a court of law] before you pass judgment on her. ▪ This is your lucky day. [=a day when something good happens to you] ◊If a day is your day, something good will happen to you on that day. ▪ You never know. Maybe today will be my day. [=maybe I will succeed, win, etc., today] ▪ I'm sorry you lost. I guess it just wasn't your day. ◊People sometimes use the phrase that'll be the day to say that they think something will not happen. ▪ “Do you think he'll ever admit he made a mistake?” “That'll be the day!”
6 [count] : a particular period of time ▪ She was the most talented actress of her day. [=during the time when she lived and worked as an actress] ▪ In my day [=when I was young], boys asked girls out on dates, not the other way around. ▪ Life was simpler in my grandmother's day, but it wasn't easier. ▪ We sell books dating from 1875 to the present day. [=today] —often plural ▪ He often spoke about his days as a soldier. ▪ I was quite an athlete in my younger days. [=when I was young] ▪ The practice dates back to the days of ancient Rome. ▪ the olden days ▪ my college days [=when I was in college] ▪ the days of stagecoaches [=when stagecoaches were used] ▪ In those days many factory workers were children. ◊The saying those were the days is sometimes used to say that a period of time in the past was pleasant and often better than the present time. ▪ When I was a kid, we spent our summers at the beach. Those were the days! ▪ In the 1960s, everything seemed possible. Those were the good old days.