need help in understanding this regex pattern for string matching [duplicate]

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• Reference - What does this regex mean? 1 answer

I found this below pattern in one snippet. As I am still learning regex I need help in understanding this pattern.

String pat="(?=.*?"+ word[i]+")"

This is used to find parts of string in a given string regardless of their position. So in the snippet string was a sentence and every word was fetched in an array.