lapsed

the girls lapsed into French.

a lapsed Catholic; a lapsed club member.

the country has lapsed into chaos.

I fear she has lapsed again.

Then the conversation lapsed and all was still and quiet.

Years had lapsed since we last met.

He soon lapsed into his previous bad habits.

if your diet has lapsed it's time you revived it.

lapse into bad habits; a team that lapsed into mediocrity halfway through the season.

He realized that his attention had lapsed and he hadn't heard the assignment.