Tea or Dinner?

What's for tea tonight?

What's for dinner tonight?

Which term should we use?

They seem to refer to the same thing: an evening meal, last of the day.

The quaint vernacular "tea" is used for the evening meal, but also the more formal sounding "dinner"?

In the old days, the midday meal, lunch, was the largest meal. In the evening, they would minimalise the diet and just have a cup of tea and some toast or some small snack.

Dinner describes the experience better for today's norms. It is the meal that requires a dining table, not a kitchen table.

Restaurants have a Dinner menu, not a Tea menu, for the evening event.

We dine when we have dinner.

So, we don't go out to a restaurant for an evening meal and call it Tea. We call it Dinner.

There's the difference.