abbabbaa

abbabbaa is a finite word formed from the binary alphabet {a, b}. In formal language theory and string algorithms, it is commonly used as an illustrative example because it combines short length with a nontrivial structure. The word has length 8 and begins with a and ends with a.

Its run-length encoding is (a,1)(b,2)(a,1)(b,2)(a,2), indicating five runs of consecutive identical symbols. It contains several notable substrings, including abba at positions 1–4 and bbaa at positions 5–8, as well as abb at 1–3, bab at 3–5, and others. The entire word is not a palindrome; its reverse is aabbabba, which differs from the original.

Because of its small size and mixed pattern, abbabbaa is useful for illustrating basic concepts in string processing, such as substring search, pattern matching, and automaton design. It may appear in teaching materials to demonstrate how algorithms handle binary strings with repeated blocks and transitions between symbols.

Related topics include binary words, pattern avoidance, and the study of factors and borders in formal languages. While abbabbaa does not denote a widely recognized object beyond being a sample word, it serves as a concrete example for analyzing properties of binary strings and for testing simple algorithms.