Is there a difference between “night” (לַיְלָה) and “evening” (עֶרֶב) in Hebrew?

Question

In Genesis 1:5, it is written,

⁵ God called the light Day, and the darkness He called Night. So the evening and the morning were the first day. ^{NKJV, ©1982}

^ה וַיִּקְרָא אֱלֹהִים לָאוֹר יוֹם וְלַחֹשֶׁךְ קָרָא לָיְלָה וַיְהִי־עֶרֶב וַיְהִי־בֹקֶר יוֹם אֶחָד

Why does the Bible use different words like עֶרֶב (erev) for evening and לַיְלָה (laila) for night when they both denote the same thing?

Answer 1

They don't denote the same thing. Just as in English 'sunset' or 'twilight' is different than 'night.'

Evening (ערב) is associated with sunset. BDB first entry:

1. a. evening, originally sunset, and hence perhaps ׳לְעֵת ע at the time of sunset

The opposite of "evening" is "morning" (בקר) "boker" - where the rising sun breaks through the darkness. BDB has:

a. end of night or b. implying the coming of dawn

Morning (בקר)is different than day (יום) 'Yom' or light (אור) 'or'

Answer 2

The Why

In the Hebrew Calendar system the beginning of the new day starts at sundown. The same could ask why English uses day and noon. Noon represents the specific time of the day. Likewise ereb in the Hebrew represents the specific time of night.