Yesterday, last night, last week, ago (A1 Vocabulary)
All four of these point BACK, to a time that is already finished. Yesterday is the day before today. Last night is the night before this morning. Last week is the week before this one. Ago works differently: it comes after a length of time and counts back from now: an hour ago, three days ago.
Yesterday, last night, last week, ago
yesterday /ˈjestərdeɪ/ — The park was very busy yesterday.
last night /ˌlæst ˈnaɪt/ — We were at home last night.
last week /ˌlæst ˈwiːk/ — Camila was in Ghafwick last week.
ago /əˈɡoʊ/ — The film was two hours ago.
Try it: Mei: Is the English test today? Lars: No, you have missed it by one day. It was ___. Finish what Lars says. (yesterday / last week / last month) Answer: yesterday — Lars says Mei is late by one day, so the test was the day before this one. The other two answers put it much further back than a single day.
Try it: Ira: You look very tired this morning. Diego: I know. I was still awake at two o'clock ___. Finish what Diego says. (last night / last month / this week) Answer: last night — Diego was still awake at two o'clock and Ira is talking to him this morning, so the two o'clock he means is the one just before it. Neither of the other answers names a night at all.
Try it: Amina: Today is Tuesday. Is the book club this week? Sofia: No, it was on Friday, ___. Finish what Sofia says. (last week / this week / last night) Answer: last week — Amina says today is Tuesday, so this week's Friday has not come yet. The Friday Sofia means is the one before this week started. And the night that has just gone was a Monday night, not a Friday.
Try it: Lars: Is Ethan still at the bank? I need him now. Mei: He was there ___, so he is very near. Finish what Mei says. (ten minutes ago / last night / last month) Answer: ten minutes ago — Mei knows Ethan is very near, so he was at the bank only minutes back. The other two answers are both much further back than that, and neither one would tell Lars where Ethan is now.