So subtle that it cannot be perceived or noticed.

A slight or gradual change that is not easily noticed.

सूक्ष्म परिवर्तन

English Usage: The imperceptible pulse of change in technology often goes unnoticed by many.

Hindi Usage: प्रौद्योगिकी में परिवर्तन की अदृश्य नाड़ी अक्सर कई लोगों द्वारा अनदेखी रह जाती है।

Impossible to perceive; very slight.

अनुपस्थित

English Usage: There was an imperceptible smile on her face that revealed her true feelings.

Hindi Usage: उसके चेहरे पर एक अनुपस्थित मुस्कान थी जो उसकी सच्ची भावनाओं को प्रकट करती थी।