Substring

In <a href="/facts/Formal_language/crDTyP8q">formal language theory</a> and <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, a substring is a contiguous sequence of <a href="/facts/Character_(computing)/X2zKLFFB">characters</a> within a <a href="/facts/String_(computer_science)/4ChJu5WS">string</a>. For instance, "the best of" is a substring of "It was the best of times". In contrast, "Itwastimes" is a subsequence of "It was the best of times", but not a substring.
Prefixes and suffixes are special cases of substrings. A prefix of a string 
 
 
 
 S
 
 
 {\displaystyle S}
 
 is a substring of 
 
 
 
 S
 
 
 {\displaystyle S}
 
 that occurs at the beginning of 
 
 
 
 S
 
 
 {\displaystyle S}
 
; likewise, a suffix of a string 
 
 
 
 S
 
 
 {\displaystyle S}
 
 is a substring that occurs at the end of 
 
 
 
 S
 
 
 {\displaystyle S}
 
.
The substrings of the string "apple" would be:
"a", "ap", "app", "appl", "apple",
"p", "pp", "ppl", "pple",
"pl", "ple",
"l", "le"
"e", "" 
(note the <a href="/facts/Empty_string/T7udJlmQ">empty string</a> at the end).

Substring open-in-new

Substring