Learn Spanish (Latin America): Por la noche cenamos en familia.

When telling time, you use de la noche for a specific hour, like son las nueve de la noche (it is 9 p.m.). But when you just mean during the night or evening in general, you use por la noche or en la noche.

Why is the word "have" missing from cenamos?

In English, we use the phrase "have dinner." Spanish has a single verb for this action: cenar (to dine or to have dinner). Because cenamos ends in -amos, it specifically means "we have dinner" all by itself without needing a separate word for "have".

Why use en familia to mean "as a family"?

En familia is a natural Spanish phrase used when an activity is done together with your relatives. If you translated "as a family" word-for-word you might guess como una familia, but en familia is the standard, everyday way to express doing things together at home.

Could I add nosotros before cenamos?

Yes, you could say nosotros cenamos, but you do not have to. The -amos ending on the verb already makes it clear that "we" are doing the action, so native speakers usually leave nosotros out.