Bigram Jaccard similarity applies the Jaccard coefficient to the bigram (2-gram) representations of two texts. Given a text $T$, let $B(T)$ be the set of distinct ordered token bigrams obtained by sliding a window of length $2$ over its tokens; for tokens $(t_1,\dots,t_n)$, $B(T)=\{(t_i,t_{i+1})\mid 1\le i\le n-1\}$. For two texts $X$ and $Y$ the bigram Jaccard similarity is $J_{2}(X,Y)=\dfrac{|B(X)\cap B(Y)|}{|B(X)\cup B(Y)|}$, taking values in $[0,1]$. Compared with unigram (bag-of-words) Jaccard, the bigram variant rewards short-range word-order agreement: two texts must reuse the same adjacent-word pairs, not just the same vocabulary, to score highly. It is reported as a lexical-overlap baseline alongside TF-IDF cosine and ROUGE-L when comparing paired drafts.