Merge branch 'ICU-21242' into ICU-21242
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
