שְׁנֵ֥י הַמְּאֹרֹ֖ת הַגְּדֹלִ֑ים
Two Great Lights
Though light was revealed on day one of creation, it was not until the fourth day that "lights" (מְּאֹרֹ֖ת moroth) were placed, or appointed, to light the earth. Though translated the same, the word here is to אוֹר a candle or mirror is to the flame that lights the room. A lamp does no good unless it is lit.
The lights are great (Hebrew: גָּדוֹל gadôl; large), that is a lot bigger and brighter than anything else in the sky, and would be a major influence to the people, plants and creatures of the planet.
It is significant that these lights are not named. God had no intention of honoring the tools he used in maintaining his creation. In His law He would condemn the worship of any created thing.