or topical sentence
a sentence that expresses the essential idea of a paragraph or larger section, usually appearing at the beginning.
Origin of topic sentence
First recorded in 1915–20
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a sentence in a paragraph that expresses the main idea or point of the whole paragraph
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
The main sentence in a paragraph, often the first sentence. It briefly conveys the essential idea of the paragraph.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.