What word does your mother always say?
also (and with more etymological propriety) deflexion, c.1600, from Latin deflexionem, noun of action from past participle stem of deflectere (see deflect). Both forms were present 17c., but the spelling with -c- has come to predominate.
deflection de·flec·tion (dĭ-flěk'shən)
A turning aside or deviation.
The deviation of an indicator in a measuring instrument, such as an electrocardiograph, from zero or from its normal position.