substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)
"He replaced the old razor blade"
"We need to replace the secretary that left a month ago"
"the insurance will replace the lost income"
"This antique vase can never be replaced"
take the place or move into the position of
"Smith replaced Miller as CEO after Miller left"
"the computer has supplanted the slide rule"
"Mary replaced Susan as the team's captain and the highest-ranked player in the school"
put in the place of another; switch seemingly equivalent items
"the con artist replaced the original with a fake Rembrandt"
"substitute regular milk for fat-free milk"
"synonyms can be interchanged without a changing the context's meaning"
To restore to a former place, position, condition, etc.; to put back
"After cleaning the living room, I carefully replaced every cushion in its original spot on the sofa."
In plain English: To replace something means to take it out and put a new one in its place.
"Please replace the old lightbulb with a new one before dinner."
Usage: Use replace when you are putting something or someone back into their original spot after they have been removed. This verb is often confused with substitute, which implies swapping one item for another rather than returning the initial one.
The word replace comes from combining the prefix re- with place. It originally meant to put something back into its original position before evolving to mean taking the place of someone or something else.