CA2, CA-2 or CA II may refer to : Carbonic anhydrase II, a human gene the United States Court of Appeals for the Second Circuit California's 2nd congressional district Hummel CA-2, an ultralight aircraft California State Route 2 Ca II, a singly-ionized calcium that produces the H and K lines, and the calcium triplet lines in the spectrum of many stars Cornu Ammonis 2, a region of the hippocampus