the act of making something different (as e.g. the size of a garment)

loosening / laxation - the act of making something less tight
tightening - the act of making something tighter
accommodation - (physiology) the automatic adjustment in focal length of the lens of the eye
adaptation - (physiology) the responsive adjustment of a sense organ (as the eye) to varying conditions (as of light)
tune - the adjustment of a radio receiver or other circuit to a required frequency

    change

the act of adjusting something to match a standard

alignment - the act of adjusting or aligning the parts of a device in relation to each other
collimation - the accurate adjustment of the line of sight of a telescope
temperament - an adjustment of the intervals (as in tuning a keyboard instrument) so that the scale can be used to play in different keys
tune-up - adjustments made to an engine to improve its performance
synchronization / synchronisation / synchronizing / synchronising - an adjustment that causes something to occur or recur in unison
voicing - the act of adjusting an organ pipe (or wind instrument) so that it conforms to the standards of tone and pitch and color

    calibration     standardization     standardisation

making or becoming suitable; adjusting to circumstances

shakedown - initial adjustments to improve the functioning or the efficiency and to bring to a more satisfactory state

    improvement     betterment     advance

an amount added or deducted on the basis of qualifying circumstances; "an allowance for profit"

cost-of-living allowance - an allowance for changes in the consumer price index
depreciation allowance - an allowance for loss due to depreciation
deduction / discount - an amount or percentage deducted
seasonal adjustment - a statistical adjustment made to accommodate predictable fluctuations as a function of the season of the year

    recompense

the process of adapting to something (such as environmental conditions)

acclimatization / acclimatisation / acclimation - adaptation to a new climate (a new temperature or altitude or environment)
dedifferentiation - the loss of specialization in form or function
domestication - adaptation to intimate association with human beings
specialization / specialisation / differentiation - (biology) the structural adaptation of some body part for a particular function

    organic process     biological process