44 synonyms for extension such as delay, add-on, amplification, continuation, and deferral. Extension is a noun, and its antonyms are retrogression and regression.
Add-on, addendum, addition, adjunct, annexe, appendage, appendix, augmentation, ell, supplement, supplementary building, and wing.
Amplification, augmentation, broadening, continuation, deepening, development, diversification, drawing out, elongation, enhancement, enlargement, expansion, growth, heightening, increase, lengthening, stretching, and widening.
Additional time, continuation, deferral, delay, increase, increased time, lengthening, longer period, more/extra time, perpetuation, postponement, prolongation, and protraction.