the sun: the star that gives light and heat, marks the hours and seasons, and orients direction
The word refers to the sun as an observable reality in the sky. It covers the sun's rising and setting as the structure of the day, its heat as a physical force, its light as the measure of time and season, and its position as a pointer of direction.
The directions "east" and "west" in Hebrew are regularly expressed through the sun: "the rising of the sun" (מִזְרַח שֶׁמֶשׁ) means east, and "the going in of the sun" (מְבוֹא הַשֶּׁמֶשׁ) means west. These are geographic idioms built from the primary sense of the word, not a separate meaning.
Because the sun is the most prominent celestial body, it appears as a target of the worship that the Torah forbids (Deuteronomy 4:19; 17:3; 2 Kings 23:11; Ezekiel 8:16) and as an image of divine permanence and glory (Psalm 72:5; 89:36; Judges 5:31; Malachi 4:2). In the prophets and apocalyptic poetry it is darkened as a sign of judgment (Isaiah 13:10; Joel 2:10; Amos 8:9). In Ecclesiastes, life "under the sun" (תַּחַת הַשֶּׁמֶשׁ) becomes a refrain for all human experience in the visible world.