Erev has two meanings. On its own it mean: evening. But in front of another time span it means: the day before. This is the main thing to know here.
Many people, including Orthodox Israel-born chief rabbis!, forget the second option and erroneously call Friday night erev shabbat. Erev shabbat, however, means: the day before Shabbat, or: Thursday night until (but not including) Friday night – the Jewish day goes from sundown to sundown – not from 00:00 – 24:00. Now, 2 more Hebrew terms:
Leil means: the eve(ning) of. So leil shabbat is: Shabbat Eve or Friday evening. Leil pesach is: Passover Eve, (the first) Passover evening.
Or also has two meanings. Or on its own it means: light. But with le in front of a day it means: the (dark) eve of that day – confusing for beginners! Or leyom rishon (of the first day) means: the Eve of Day One, Saterday evening. The first day of the Hebrew week is Sunday! Or leyom shishi means: the Eve of Day Six, Thursday evening.
Now, look at the following examples. If you don’t understand any of them, look at the above rules again. Print and cut out the table lines and fold the English to the back of the Hebrew and quiz yourself until you get all of them right.
|Erev shabbat||Thursday evening – Friday evening|
|Erev shel shabbat||Friday evening / Shabbat Eve|
|Leil shabbat||Friday evening / Shabbat Eve|
|Or le-erev shabbat||Thursday evening|
|Leil erev shabbat||Thursday evening|
|Erev pesach||The 24 hours before Passover Eve|
|Erev shel pesach||Passover evening / Eve|
|Leil pesach||Passover evening / Eve|
|Or le-erev pesach||The evening before Passover|
|Leil erev pesach||The evening before Passover|
|Yom rishon||Saturday night until Sunday night|
|Yom sheni||Sunday night until Monday night|
|Erev yom sheni||Saturday night until Sunday night|
|Erev shel yom sheni||Sunday evening|
|Leil yom sheni||Sunday evening|
|Or le-erev yom sheni||Saturday evening|
|Leil erev yom sheni||Saturday evening|
Erev chag semei’ach!