fect=作る、する

defect / 離れて作る→理想と離れたものを作る→欠陥、欠点

cf. Several defects were found in the design of the ship.

affect / 目指して作る→影響する、〜のふりをする

cf. She affected a calmness she did not feel.

infect / 中に入って作る→伝染する、感染する

cf. This virus infected thousands of computers within days.