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?