[ah fohr-ti-oh-ree; English ey fawr-shee-awr-ahy, ey fohr-shee-ohr-ahy]
for a still stronger reason; even more certain; all the more.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
for similar but more convincing reasonsif Britain cannot afford a space programme, then, a fortiori, neither can India
Word Origin for a fortiori
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