Imperceptibly

Bad manners shade imperceptibly into crime: both have their roots in an absence of concern for others.

Tom nodded his head almost imperceptibly.

While he was thus amusing her in the noon-day heat, with their flocks around them reposing in the shade, Chloe imperceptibly fell asleep.

Earth's axis has shifted imperceptibly.

No one noticed that he had moved imperceptibly backwards.

It often happens that the most important results in the natural world are brought about by causes which operate silently, if not imperceptibly.

The moon moved imperceptibly towards setting.

Which means that at the moment Raven entered her, a very small hypodermic needle slipped imperceptibly into the engorged frontal vein of his penis, automatically shooting a cocktail of powerful narcotics and depressants into his bloodstream.