diff --git a/docs/userguide/boundaryanalysis/index.md b/docs/userguide/boundaryanalysis/index.md
index dc08e77..2e8dd6e 100644
--- a/docs/userguide/boundaryanalysis/index.md
+++ b/docs/userguide/boundaryanalysis/index.md
@@ -193,7 +193,7 @@
 
 For concurrent break iteration, each thread must use its own break iterator.
 These can be obtained by creating separate break iterators of the desired type,
-or by initially creating a primary break iterator and then creating a clone for
+or by initially creating a main break iterator and then creating a clone for
 each thread.
 
 ### Line Breaking Strictness, a CSS Property