Here the word points at people rather than at language. It covers Arabs and Jews today, and in history books it also covers the Babylonians, the Assyrians and the Phoenicians. The grouping was made by scholars, and it was built on the languages these peoples spoke, so it is a label about language history more than about how anyone looks. In the Bible the same group is traced back to Shem, a son of Noah, and books with a religious frame sometimes say Semitic to mean the descendants of Shem. Older dictionaries call this a race; peoples is the ordinary word for it now.

This sense is only about language. Semitic names a group of languages that are related to one another, in the way Spanish and Italian are related. Arabic and Hebrew are the two largest living members. Amharic, spoken in Ethiopia, and Maltese also belong to the group. Older members such as Akkadian and Phoenician are no longer spoken by anyone. You will meet the word most often in the fixed phrase Semitic languages, in history books and in language classes. Calling a language Semitic says nothing about the religion of the people who speak it.

This is the narrow use. The wide sense covers Arabs and Jews together, but here the word points at Jewish people only. A reader usually meets this narrow reading inside the longer word anti-Semitic, which means showing hatred towards Jewish people. On its own, Semitic in this sense turns up mostly in older writing and in careful historical prose, where the plain words Jewish and Jewish people are the ordinary modern choice. Because the same form carries both the wide and the narrow meaning, the surrounding sentence is what tells you which one is meant.