food: whatever is eaten to nourish and sustain life
This is the ordinary Greek word for food, whatever a person eats to stay alive and strong. It stretches across a meal, a daily diet, provisions bought at the market, the rations a master doles out, and the keep a worker earns. Everywhere it appears in the New Testament it stays close to that plain center: nourishment that sustains the body.
Where other food words name a particular item, this word names the function. Bread (ἄρτος) is the staple loaf, and βρῶμα is the thing eaten as a dish or portion, but this word is food seen as what keeps life going. That is why it pairs so naturally with life itself, as in the question "is not life more than food?"
The letter to the Hebrews stretches the word into a picture: "solid food" for those mature enough to handle harder teaching, set against "milk" for beginners. The word still means food; the writer simply borrows the everyday experience of eating to describe growing up in understanding.