The phrasal verb "creep in" is predominantly used in informal speech, often implying the subtle or gradual occurrence of something. It generally describes the way something unwanted or unexpected begins to appear or make itself known, often without people noticing at first. This verb might be used in contexts such as describing how doubts, fears, or mistakes gradually introduce themselves into a situation—e.g., "Errors started to creep in after the new system was implemented." It conveys a slightly negative connotation of invasion or infiltration and is less likely to be used in formal writing unless specific stylistic effects are desired. The imagery of "creep" suggests quiet and stealthy movement, further illustrating the gradual characteristic the phrasal verb connotes.
B2
UpperIntermediate
1. To gradually become noticeable; to start to be felt or seen slowly.
Doubt began to creep in as the project faced more challenges than anticipated.
Fatigue crept in after hours of continuous work.
2. To start to become part of something; to infiltrate slowly or subtly.
New methods began to creep in, changing the way traditional work was done.
Errors crept in through the new system implementation.