debian/ubuntu: apt-get install wdiff macosx: fink install wdiff
From apt-cache show:
wdiff’ is a front-end to GNU diff. It compares two files, finding which words have been deleted or added to the first in order to create the second. It has many output formats and interacts well with terminals and pagers (notably with less'). wdiff’ is particularly useful when two texts differ only by a few words and paragraphs have been refilled.