diff --git a/R/calculate_study_day.R b/R/calculate_study_day.R
index 527f1dd2..f50cbaa5 100644
--- a/R/calculate_study_day.R
+++ b/R/calculate_study_day.R
@@ -15,10 +15,10 @@
 #' day.
 #' @param study_day_var the new study day variable name in the output. For
 #' example, AESTDY for AE domain and CMSTDY for CM domain.
-#' @param merge_key character to represents the merging key between `sdtm_in` and
+#' @param merge_key Character to represents the merging key between `sdtm_in` and
 #' `dm_domain`.
 #'
-#' @return a data.frame that takes all columns from `sdtm_in` and a new variable
+#' @return Data frame that takes all columns from `sdtm_in` and a new variable
 #' to represent the calculated study day.
 #'
 #' @export