gradually

piecemeal

In separate stages

• phasedIntroduced or removed incrementally
• staggeredShocked or unevenly spaced
• sequentialOccurring in succession

successive · iterative · cumulative · additive · accumulative · progressive · stepwise · tiered · staged · layered

slow

Lacking in speed

• steadyFixed, not fluctuating
• measuredCarefully considered, unhurried
• deliberateConsciously chosen, not accidental

unhurried · leisurely · methodical · gentle · moderate · languid · plodding · sedate · easygoing · relaxed

imperceptible

Cannot be sensed

• faintWeak and indistinct
• slightMinor or thin
• gentleSoft and kind

soft · barely · scarcely · indistinct · unnoticed · insensible · quietly · silently · invisibly · stealthily

diminish

To make smaller

• declineDecrease or refuse
• waneDecrease gradually
• subsideDecrease in intensity

lessen · shrink · fade · ebb · dwindle · taper · recede · weaken · abate · erode

steady

Fixed, not fluctuating

• constantFixed, unvarying quantity
• sustainedKept up continuously
• unbrokenNot damaged or interrupted

seamless · uninterrupted · persistent · ongoing · continual · relentless · unfaltering · even · smooth · flowing

shift

Movement or work period

• transitionChange from one state
• transformChange completely in form
• evolveChange gradually over time

develop · mature · unfold · emerge · morph · adjust · adapt · progress · ripen · mellow

grow

Increase in size

• buildCreate a structure
• escalateIncrease in severity
• intensifyIncrease in degree

expand · mount · swell · rise · climb · accumulate · amplify · strengthen · heighten · deepen

• gradual phrasesbit by bit, little by little, step by step, one by one, piece by piece
• timesecond, minute, hour, day, seconds
• time wordsminute, hour, day, now, soon
• adverbsquickly, slowly, very, really, now
• moderationmoderation, in moderation, restraint, self-control, moderately
• mental adverbsmentally, cognitively, consciously, unconsciously, subconsciously