Hun er femti i år.

Norwegian usually states age with å være + a number, so Hun er femti is a normal way to say someone’s age.

You can also say Hun er femti år and, more explicitly, Hun er femti år gammel, but everyday Norwegian often leaves out år and gammel when the meaning is obvious.

I år means this year.

In an age sentence, it places the age within the current year rather than only at this exact moment. So it is talking about her age in the course of this year.

By itself, it can cover either idea, depending on context.

It often means that 50 is her age this year, so she may already have had her birthday, or she may reach that age later in the year. If you want to make the birthday change clearer, Norwegian often uses blir instead: Hun blir femti i år.

Er states the age as a fact: she is fifty this year.

Blir focuses on the change: she turns fifty this year.

So both can be natural, but they are slightly different in emphasis:

• Hun er femti i år = her age this year is 50
• Hun blir femti i år = she will reach 50 this year

Yes, people would understand it, but it sounds a bit repetitive because år appears twice: once in femti år and again in i år.

That is why Hun er femti i år sounds more natural. Norwegian often avoids repeating år unnecessarily.

Yes. You can say I år er hun femti.

This follows the normal Norwegian verb-second rule: when a time expression comes first, the finite verb still comes second. So:

• Hun er femti i år
• I år er hun femti

But not I år hun er femti.

No. Femti stays the same.

Numbers do not agree with gender or person in this kind of sentence:

• Hun er femti
• Han er femti
• Læreren er femti

The number femti does not change.