to chalk it up to

Example 1:

Linda has been very irritable lately. She's not as friendly as she used to be and she doesn't always respond to questions in a polite way. Her rude behavior has made her co-workers uncomfortable, but they know she is having a hard time in her personal life because of her divorce. We know she's really a good person and this behavior isn't normal; we just chalk it up to stress.

Example 2:

Nathan always knows what to do in any situation. In an emergency, he is calm helps others. In the office, he is a master at solving problems. At a party, he's the one getting people talking and dancing. He just always knows what to do! When I asked him for his secret, he just says, "Chalk it up to experience."

Meaning:
The expression chalk it up to something is used to explain the cause of a result. The something is the cause.

In the first example, Linda is rude and not behaving like herself. Her coworkers know that she has a lot of stress in her life, so her bad behavior is caused by the stress.

In the second example, Nathan knows everything about everything! All of his knowledge is caused by his life experience.

This idiom can be found in the LSI textbook Speaking Transitions. This book is used at LSI schools in the level 4 Listening/Speaking classes. For more information, please visit: www.languagesystems.com