In the 1998 film "Saving Private Ryan," actor Tom Hanks plays the part of Captain Miller. The fictional Captain Miller was an English teacher before becoming a soldier and fighting in World War II.
In one scene, Captain Miller describes how he has changed:
"So I guess I've changed some. Sometimes I wonder if I've changed so much my wife is even gonna recognize me whenever it is I get back to her, and how I'll ever be able to, to tell her about days like today."
These lines give you an excellent example of how speakers show uncertainty in everyday speech.
In the first sentence, Miller used a common grammatical structure: verb + a noun clause.
In today's report, we will explore this structure and show you how speakers use it in everyday situations.
Noun Clauses
Noun clauses are groups of words that act as a noun. They often begin with "that" or a word beginning with "wh," such as "where," "when," "why," or "what." Here are two examples:
I think that she is mad at me.
I wonder where he went?
In the examples, the main parts of the sentences are the words "I think" and "I wonder." The verbs are followed by noun clauses: "that she is mad at me," and "where he went."
By the way, the word "that" does not add any meaning in these types of clauses, so it is often dropped. Instead of saying "I think that she is mad at me," speakers might say, "I think she is mad at me."
If you want to learn more about why the word "that" disappears from sentences, you should read our previous Everyday Grammar story "The Mystery of the Disappearing That."
Showing Uncertainty with Verb + Noun Clause 
Americans often use a verb + noun clause structure to show uncertainty.
The verb shows uncertainty, and the noun clause shows the idea.