Questions & Answers about Þetta eru tveir tómatar.
Why do we use tveir instead of tvær or tvö?
Why is Þetta used for "These" here? Doesn't Þetta mean "This"?
How can I tell that tómatar is a masculine noun?
Why is the phrase tveir tómatar in the nominative case?
The verb eru comes from vera (to be). This verb acts like an equals sign rather than an action. Because there is no action being done to the tomatoes, they stay in the basic dictionary form, which is the nominative case.