diff --git a/R/define.R b/R/define.R
index db421022..ac73ec65 100644
--- a/R/define.R
+++ b/R/define.R
@@ -18,6 +18,10 @@
 
 #' Define enrollment rate
 #'
+#' The function define subject enrollment rate for a study.
+#' It also supports stratified design that have different enrollment rate in
+#' each stratum.
+#'
 #' @param duration A numeric vector of piecewise study duration interval.
 #' @param rate A numeric vector of enrollment rate in each `duration`.
 #' @param stratum A character vector of stratum name.
@@ -74,7 +78,7 @@ define_enroll_rate <- function(
   df
 }
 
-#' Define fail rate
+#' Define failure rate
 #'
 #' The function define subject failure rate for a study with two treatment groups.
 #' It also supports stratified design that have different failure rate in
diff --git a/man/define_enroll_rate.Rd b/man/define_enroll_rate.Rd
index 0893cd5f..3b65d0df 100644
--- a/man/define_enroll_rate.Rd
+++ b/man/define_enroll_rate.Rd
@@ -17,7 +17,9 @@ define_enroll_rate(duration, rate, stratum = "All")
 An \code{enroll_rate} data frame.
 }
 \description{
-Define enrollment rate
+The function define subject enrollment rate for a study.
+It also supports stratified design that have different enrollment rate in
+each stratum.
 }
 \examples{
 # Define enroll rate without stratum
diff --git a/man/define_fail_rate.Rd b/man/define_fail_rate.Rd
index 51af14a0..b91278e0 100644
--- a/man/define_fail_rate.Rd
+++ b/man/define_fail_rate.Rd
@@ -2,7 +2,7 @@
 % Please edit documentation in R/define.R
 \name{define_fail_rate}
 \alias{define_fail_rate}
-\title{Define fail rate}
+\title{Define failure rate}
 \usage{
 define_fail_rate(duration, fail_rate, dropout_rate, hr = 1, stratum = "All")
 }