updated README.md

Tsung-Wei Huang · Tsung-Wei Huang · commit ffa45011f69b · 2018-06-13T16:33:18.000-04:00
diff --git a/README.md b/README.md
@@ -295,7 +295,7 @@ The table below summarizes its methods.
 
 ### *precede*
 
-The method `precede` is the basic function to add a precedence between two tasks.
+The method `precede` is the basic building block to add a precedence between two tasks.
 
 <img align="right" width="20%" src="image/precede.png">
 
