Today we mark the bicentennial of the birth of Jean Louis Rodolphe Agassiz, one of the premier scientists of his day. Although today he is celebrated as a zoologist, glaciologist, and geologist, he considered himself primarily an ichthyologist. (来源：英语学习门户网站EnglishCN.com)

A zoologist is concerned with the classification, properties, and vital phenomena of animals; a glaciologist studies snow or ice accumulation, glaciation, or glacial epochs; a geologist deals with the history of the earth and its life, especially as recorded in rocks. And then there's the ichthyologist, who works with fishes.

The history of the words zoologist, glaciologist, and geologist are all pretty straightforward. As used here, the noun suffix –ist denotes "one who practices, studies, or specializes in a specified art or science, or in a particular field of knowledge or particular skill." Glaciologist traces to the Latin noun glacies, meaning "ice;" and zoologist and geologist have ancestors in the Greek zoe and ge (meaning "life" and "earth," respectively). Likewise, the ichthy in ichthyologist meant "fish" in Greek.